图中C所在省南部某地近二十年来生态环境明显改善，根据下表资料C所在地区农村生活用能构成的变化，推测其主要原因是<table style="PADDING-BOTTOM: 0pt; PADDING-LEFT: 0pt; PADDING-RIGHT: 0pt; BORDER-COLLAPSE: collapse; MARGIN-LEFT: -7.6pt; PADDING-TOP: 0pt; mso-table-layout-alt: fixed" align="center"><tbody><tr style="HEIGHT: 23.25pt"><td style="BORDER-BOTTOM: rgb(0,0,0) 0.75pt solid; BORDER-LEFT: rgb(0,0,0) 0.75pt solid; PADDING-BOTTOM: 0pt; PADDING-LEFT: 0pt; WIDTH: 40.1pt; PADDING-RIGHT: 0pt; BORDER-TOP: rgb(0,0,0) 0.75pt solid; BORDER-RIGHT: rgb(0,0,0) 0.75pt solid; PADDING-TOP: 0pt; mso-border-left-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-right-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-top-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-bottom-alt: 0.7500pt solid rgb(0, 0, 0)" valign="center" width="53"></td><td style="BORDER-BOTTOM: rgb(0,0,0) 0.75pt solid; BORDER-LEFT: medium none; PADDING-BOTTOM: 0pt; PADDING-LEFT: 0pt; WIDTH: 50.55pt; PADDING-RIGHT: 0pt; BORDER-TOP: rgb(0,0,0) 0.75pt solid; BORDER-RIGHT: rgb(0,0,0) 0.75pt solid; PADDING-TOP: 0pt; mso-border-left-alt: none; mso-border-right-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-top-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-bottom-alt: 0.7500pt solid rgb(0, 0, 0)" valign="center" width="67">秸秆</td><td style="BORDER-BOTTOM: rgb(0,0,0) 0.75pt solid; BORDER-LEFT: medium none; PADDING-BOTTOM: 0pt; PADDING-LEFT: 0pt; WIDTH: 42.75pt; PADDING-RIGHT: 0pt; BORDER-TOP: rgb(0,0,0) 0.75pt solid; BORDER-RIGHT: rgb(0,0,0) 0.75pt solid; PADDING-TOP: 0pt; mso-border-left-alt: none; mso-border-right-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-top-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-bottom-alt: 0.7500pt solid rgb(0, 0, 0)" valign="center" width="57">薪柴</td><td style="BORDER-BOTTOM: rgb(0,0,0) 0.75pt solid; BORDER-LEFT: medium none; PADDING-BOTTOM: 0pt; PADDING-LEFT: 0pt; WIDTH: 47.8pt; PADDING-RIGHT: 0pt; BORDER-TOP: rgb(0,0,0) 0.75pt solid; BORDER-RIGHT: rgb(0,0,0) 0.75pt solid; PADDING-TOP: 0pt; mso-border-left-alt: none; mso-border-right-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-top-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-bottom-alt: 0.7500pt solid rgb(0, 0, 0)" valign="center" width="63">煤炭</td><td style="BORDER-BOTTOM: rgb(0,0,0) 0.75pt solid; BORDER-LEFT: medium none; PADDING-BOTTOM: 0pt; PADDING-LEFT: 0pt; WIDTH: 44.4pt; PADDING-RIGHT: 0pt; BORDER-TOP: rgb(0,0,0) 0.75pt solid; BORDER-RIGHT: rgb(0,0,0) 0.75pt solid; PADDING-TOP: 0pt; mso-border-left-alt: none; mso-border-right-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-top-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-bottom-alt: 0.7500pt solid rgb(0, 0, 0)" valign="center" width="59">沼气</td><td style="BORDER-BOTTOM: rgb(0,0,0) 0.75pt solid; BORDER-LEFT: medium none; PADDING-BOTTOM: 0pt; PADDING-LEFT: 0pt; WIDTH: 48.35pt; PADDING-RIGHT: 0pt; BORDER-TOP: rgb(0,0,0) 0.75pt solid; BORDER-RIGHT: rgb(0,0,0) 0.75pt solid; PADDING-TOP: 0pt; mso-border-left-alt: none; mso-border-right-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-top-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-bottom-alt: 0.7500pt solid rgb(0, 0, 0)" valign="center" width="64">小水电</td><td style="BORDER-BOTTOM: rgb(0,0,0) 0.75pt solid; BORDER-LEFT: medium none; PADDING-BOTTOM: 0pt; PADDING-LEFT: 0pt; WIDTH: 34.45pt; PADDING-RIGHT: 0pt; BORDER-TOP: rgb(0,0,0) 0.75pt solid; BORDER-RIGHT: rgb(0,0,0) 0.75pt solid; PADDING-TOP: 0pt; mso-border-left-alt: none; mso-border-right-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-top-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-bottom-alt: 0.7500pt solid rgb(0, 0, 0)" valign="center" width="45">其他</td></tr><tr style="HEIGHT: 12.75pt"><td style="BORDER-BOTTOM: rgb(0,0,0) 0.75pt solid; BORDER-LEFT: rgb(0,0,0) 0.75pt solid; PADDING-BOTTOM: 0pt; PADDING-LEFT: 0pt; WIDTH: 40.1pt; PADDING-RIGHT: 0pt; BORDER-TOP: medium none; BORDER-RIGHT: rgb(0,0,0) 0.75pt solid; PADDING-TOP: 0pt; mso-border-left-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-right-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-top-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-bottom-alt: 0.7500pt solid rgb(0, 0, 0)" valign="center" width="53">1987年</td><td style="BORDER-BOTTOM: rgb(0,0,0) 0.75pt solid; BORDER-LEFT: medium none; PADDING-BOTTOM: 0pt; PADDING-LEFT: 0pt; WIDTH: 50.55pt; PADDING-RIGHT: 0pt; BORDER-TOP: medium none; BORDER-RIGHT: rgb(0,0,0) 0.75pt solid; PADDING-TOP: 0pt; mso-border-left-alt: none; mso-border-right-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-top-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-bottom-alt: 0.7500pt solid rgb(0, 0, 0)" valign="center" width="67">50.3%</td><td style="BORDER-BOTTOM: rgb(0,0,0) 0.75pt solid; BORDER-LEFT: medium none; PADDING-BOTTOM: 0pt; PADDING-LEFT: 0pt; WIDTH: 42.75pt; PADDING-RIGHT: 0pt; BORDER-TOP: medium none; BORDER-RIGHT: rgb(0,0,0) 0.75pt solid; PADDING-TOP: 0pt; mso-border-left-alt: none; mso-border-right-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-top-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-bottom-alt: 0.7500pt solid rgb(0, 0, 0)" valign="center" width="57">32.4%</td><td style="BORDER-BOTTOM: rgb(0,0,0) 0.75pt solid; BORDER-LEFT: medium none; PADDING-BOTTOM: 0pt; PADDING-LEFT: 0pt; WIDTH: 47.8pt; PADDING-RIGHT: 0pt; BORDER-TOP: medium none; BORDER-RIGHT: rgb(0,0,0) 0.75pt solid; PADDING-TOP: 0pt; mso-border-left-alt: none; mso-border-right-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-top-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-bottom-alt: 0.7500pt solid rgb(0, 0, 0)" valign="center" width="63">10.3%</td><td style="BORDER-BOTTOM: rgb(0,0,0) 0.75pt solid; BORDER-LEFT: medium none; PADDING-BOTTOM: 0pt; PADDING-LEFT: 0pt; WIDTH: 44.4pt; PADDING-RIGHT: 0pt; BORDER-TOP: medium none; BORDER-RIGHT: rgb(0,0,0) 0.75pt solid; PADDING-TOP: 0pt; mso-border-left-alt: none; mso-border-right-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-top-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-bottom-alt: 0.7500pt solid rgb(0, 0, 0)" valign="center" width="59">0.5%</td><td style="BORDER-BOTTOM: rgb(0,0,0) 0.75pt solid; BORDER-LEFT: medium none; PADDING-BOTTOM: 0pt; PADDING-LEFT: 0pt; WIDTH: 48.35pt; PADDING-RIGHT: 0pt; BORDER-TOP: medium none; BORDER-RIGHT: rgb(0,0,0) 0.75pt solid; PADDING-TOP: 0pt; mso-border-left-alt: none; mso-border-right-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-top-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-bottom-alt: 0.7500pt solid rgb(0, 0, 0)" valign="center" width="64">0.8%</td><td style="BORDER-BOTTOM: rgb(0,0,0) 0.75pt solid; BORDER-LEFT: medium none; PADDING-BOTTOM: 0pt; PADDING-LEFT: 0pt; WIDTH: 34.45pt; PADDING-RIGHT: 0pt; BORDER-TOP: medium none; BORDER-RIGHT: rgb(0,0,0) 0.75pt solid; PADDING-TOP: 0pt; mso-border-left-alt: none; mso-border-right-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-top-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-bottom-alt: 0.7500pt solid rgb(0, 0, 0)" valign="center" width="45">5.7%</td></tr><tr style="HEIGHT: 19.65pt"><td style="BORDER-BOTTOM: rgb(0,0,0) 0.75pt solid; BORDER-LEFT: rgb(0,0,0) 0.75pt solid; PADDING-BOTTOM: 0pt; PADDING-LEFT: 0pt; WIDTH: 40.1pt; PADDING-RIGHT: 0pt; BORDER-TOP: medium none; BORDER-RIGHT: rgb(0,0,0) 0.75pt solid; PADDING-TOP: 0pt; mso-border-left-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-right-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-top-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-bottom-alt: 0.7500pt solid rgb(0, 0, 0)" valign="center" width="53">2007年</td><td style="BORDER-BOTTOM: rgb(0,0,0) 0.75pt solid; BORDER-LEFT: medium none; PADDING-BOTTOM: 0pt; PADDING-LEFT: 0pt; WIDTH: 50.55pt; PADDING-RIGHT: 0pt; BORDER-TOP: medium none; BORDER-RIGHT: rgb(0,0,0) 0.75pt solid; PADDING-TOP: 0pt; mso-border-left-alt: none; mso-border-right-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-top-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-bottom-alt: 0.7500pt solid rgb(0, 0, 0)" valign="center" width="67">20.5%</td><td style="BORDER-BOTTOM: rgb(0,0,0) 0.75pt solid; BORDER-LEFT: medium none; PADDING-BOTTOM: 0pt; PADDING-LEFT: 0pt; WIDTH: 42.75pt; PADDING-RIGHT: 0pt; BORDER-TOP: medium none; BORDER-RIGHT: rgb(0,0,0) 0.75pt solid; PADDING-TOP: 0pt; mso-border-left-alt: none; mso-border-right-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-top-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-bottom-alt: 0.7500pt solid rgb(0, 0, 0)" valign="center" width="57">10.8%</td><td style="BORDER-BOTTOM: rgb(0,0,0) 0.75pt solid; BORDER-LEFT: medium none; PADDING-BOTTOM: 0pt; PADDING-LEFT: 0pt; WIDTH: 47.8pt; PADDING-RIGHT: 0pt; BORDER-TOP: medium none; BORDER-RIGHT: rgb(0,0,0) 0.75pt solid; PADDING-TOP: 0pt; mso-border-left-alt: none; mso-border-right-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-top-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-bottom-alt: 0.7500pt solid rgb(0, 0, 0)" valign="center" width="63">15.4%</td><td style="BORDER-BOTTOM: rgb(0,0,0) 0.75pt solid; BORDER-LEFT: medium none; PADDING-BOTTOM: 0pt; PADDING-LEFT: 0pt; WIDTH: 44.4pt; PADDING-RIGHT: 0pt; BORDER-TOP: medium none; BORDER-RIGHT: rgb(0,0,0) 0.75pt solid; PADDING-TOP: 0pt; mso-border-left-alt: none; mso-border-right-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-top-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-bottom-alt: 0.7500pt solid rgb(0, 0, 0)" valign="center" width="59">35.3%</td><td style="BORDER-BOTTOM: rgb(0,0,0) 0.75pt solid; BORDER-LEFT: medium none; PADDING-BOTTOM: 0pt; PADDING-LEFT: 0pt; WIDTH: 48.35pt; PADDING-RIGHT: 0pt; BORDER-TOP: medium none; BORDER-RIGHT: rgb(0,0,0) 0.75pt solid; PADDING-TOP: 0pt; mso-border-left-alt: none; mso-border-right-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-top-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-bottom-alt: 0.7500pt solid rgb(0, 0, 0)" valign="center" width="64">15.2%</td><td style="BORDER-BOTTOM: rgb(0,0,0) 0.75pt solid; BORDER-LEFT: medium none; PADDING-BOTTOM: 0pt; PADDING-LEFT: 0pt; WIDTH: 34.45pt; PADDING-RIGHT: 0pt; BORDER-TOP: medium none; BORDER-RIGHT: rgb(0,0,0) 0.75pt solid; PADDING-TOP: 0pt; mso-border-left-alt: none; mso-border-right-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-top-alt: 0.7500pt solid rgb(0, 0, 0); mso-border-bottom-alt: 0.7500pt solid rgb(0, 0, 0)" valign="center" width="45">2.8%</td></tr></tbody></table>