大学英语：The death rate from the disease has been increasing at an alarming speed for the past thirty ye

　　2. The death rate from the disease has been increasing at an alarming speed for the past thirty years.

　　本句中的时态是现在完成进行时，由has (have) been加现在分词构成，主要表现以前这一段时间里一直在进行的一个动作，这个动作也可能仍然在进行，如：

　　1)What book have you been reading recently? (你最近在看什么书?)

　　2)How have you been getting on with your work? (工作进行得怎么样?)

　　3)All these years they have been contributing articles to our newspaper. (这些年来他们一直为我们报纸写稿。)

　　at an alarming speed的意思是“以惊人的速度”

　　1)We are driving at the speed of 60 miles an hour. (我们正以每小时60英里的速度行驶。)

　　2)He is running at top speed. (他正以最快速度奔跑。)

　　3)Tom is working at it at full speed. (汤姆正在拼命地干。)

　　4)He found the small town changing at an astonishing speed. (他发现那个小城正以惊人的速度变化着。)