题目

 We had different students in some classes, so _____ was a struggle for me to remember all the faces and names.     A. it                           B. that                       C. this                       D. which 答案：A物体从高H处自由落下，最后1秒内运动位移是H.求⑴物体下落的时间. ⑵物体下落的高度H。（g="10" m/s2）)