题目

In today’s competitive economy, ______ everyone is trying to do more with less, you’ve got to figure out a way to profit from the very beginning. A. which      B. that      C. how      D. where 答案：D 从一定高度的气球上自由落下两个物体,第一个物体下落一秒后,第二个物体开始下落,两物体用长93.1m的绳连接在一起.第二个物体下落到绳被拉紧的时间是（g=9.8m/s2）A  8s         B  8.5s     C     9s           D  10s