(2011～2012、河北五校联盟模拟)某学生四次模拟考试时，其英语作文的减分情况如下表：<table style="BORDER-BOTTOM: medium none; BORDER-LEFT: medium none; BORDER-COLLAPSE: collapse; BORDER-TOP: medium none; BORDER-RIGHT: medium none; mso-table-layout-alt: fixed; mso-border-alt: solid windowtext .5pt; mso-padding-alt: 0cm 5.4pt 0cm 5.4pt; mso-border-insideh: .5pt solid windowtext; mso-border-insidev: .5pt solid windowtext" border="1" cellspacing="0" cellpadding="0" _dj="MsoNormalTable"><tbody><tr style="HEIGHT: 34.05pt; mso-yfti-irow: 0; mso-yfti-firstrow: yes"><td style="BORDER-BOTTOM: windowtext 1pt solid; BORDER-LEFT: windowtext 1pt solid; PADDING-BOTTOM: 0cm; BACKGROUND-COLOR: transparent; PADDING-LEFT: 5.4pt; WIDTH: 105.45pt; PADDING-RIGHT: 5.4pt; HEIGHT: 34.05pt; BORDER-TOP: windowtext 1pt solid; BORDER-RIGHT: windowtext 1pt solid; PADDING-TOP: 0cm; mso-border-alt: solid windowtext .5pt" width="141">考试次数x</td><td style="BORDER-BOTTOM: windowtext 1pt solid; BORDER-LEFT: #000000; PADDING-BOTTOM: 0cm; BACKGROUND-COLOR: transparent; PADDING-LEFT: 5.4pt; WIDTH: 50.3pt; PADDING-RIGHT: 5.4pt; HEIGHT: 34.05pt; BORDER-TOP: windowtext 1pt solid; BORDER-RIGHT: windowtext 1pt solid; PADDING-TOP: 0cm; mso-border-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt" width="67">1</td><td style="BORDER-BOTTOM: windowtext 1pt solid; BORDER-LEFT: #000000; PADDING-BOTTOM: 0cm; BACKGROUND-COLOR: transparent; PADDING-LEFT: 5.4pt; WIDTH: 38.25pt; PADDING-RIGHT: 5.4pt; HEIGHT: 34.05pt; BORDER-TOP: windowtext 1pt solid; BORDER-RIGHT: windowtext 1pt solid; PADDING-TOP: 0cm; mso-border-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt" width="51">2</td><td style="BORDER-BOTTOM: windowtext 1pt solid; BORDER-LEFT: #000000; PADDING-BOTTOM: 0cm; BACKGROUND-COLOR: transparent; PADDING-LEFT: 5.4pt; WIDTH: 38.25pt; PADDING-RIGHT: 5.4pt; HEIGHT: 34.05pt; BORDER-TOP: windowtext 1pt solid; BORDER-RIGHT: windowtext 1pt solid; PADDING-TOP: 0cm; mso-border-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt" width="51">3</td><td style="BORDER-BOTTOM: windowtext 1pt solid; BORDER-LEFT: #000000; PADDING-BOTTOM: 0cm; BACKGROUND-COLOR: transparent; PADDING-LEFT: 5.4pt; WIDTH: 50.3pt; PADDING-RIGHT: 5.4pt; HEIGHT: 34.05pt; BORDER-TOP: windowtext 1pt solid; BORDER-RIGHT: windowtext 1pt solid; PADDING-TOP: 0cm; mso-border-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt" width="67">4</td></tr><tr style="HEIGHT: 33.55pt; mso-yfti-irow: 1; mso-yfti-lastrow: yes"><td style="BORDER-BOTTOM: windowtext 1pt solid; BORDER-LEFT: windowtext 1pt solid; PADDING-BOTTOM: 0cm; BACKGROUND-COLOR: transparent; PADDING-LEFT: 5.4pt; WIDTH: 105.45pt; PADDING-RIGHT: 5.4pt; HEIGHT: 33.55pt; BORDER-TOP: #000000; BORDER-RIGHT: windowtext 1pt solid; PADDING-TOP: 0cm; mso-border-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt" width="141">所减分数y</td><td style="BORDER-BOTTOM: windowtext 1pt solid; BORDER-LEFT: #000000; PADDING-BOTTOM: 0cm; BACKGROUND-COLOR: transparent; PADDING-LEFT: 5.4pt; WIDTH: 50.3pt; PADDING-RIGHT: 5.4pt; HEIGHT: 33.55pt; BORDER-TOP: #000000; BORDER-RIGHT: windowtext 1pt solid; PADDING-TOP: 0cm; mso-border-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt" width="67">4.5</td><td style="BORDER-BOTTOM: windowtext 1pt solid; BORDER-LEFT: #000000; PADDING-BOTTOM: 0cm; BACKGROUND-COLOR: transparent; PADDING-LEFT: 5.4pt; WIDTH: 38.25pt; PADDING-RIGHT: 5.4pt; HEIGHT: 33.55pt; BORDER-TOP: #000000; BORDER-RIGHT: windowtext 1pt solid; PADDING-TOP: 0cm; mso-border-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt" width="51">4</td><td style="BORDER-BOTTOM: windowtext 1pt solid; BORDER-LEFT: #000000; PADDING-BOTTOM: 0cm; BACKGROUND-COLOR: transparent; PADDING-LEFT: 5.4pt; WIDTH: 38.25pt; PADDING-RIGHT: 5.4pt; HEIGHT: 33.55pt; BORDER-TOP: #000000; BORDER-RIGHT: windowtext 1pt solid; PADDING-TOP: 0cm; mso-border-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt" width="51">3</td><td style="BORDER-BOTTOM: windowtext 1pt solid; BORDER-LEFT: #000000; PADDING-BOTTOM: 0cm; BACKGROUND-COLOR: transparent; PADDING-LEFT: 5.4pt; WIDTH: 50.3pt; PADDING-RIGHT: 5.4pt; HEIGHT: 33.55pt; BORDER-TOP: #000000; BORDER-RIGHT: windowtext 1pt solid; PADDING-TOP: 0cm; mso-border-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt" width="67">2.5</td></tr></tbody></table>显然所减分数y与模拟考试次数x之间有较好的线性相关关系，则其线性回归方程为(　　)