题目

A local radio said that several eruptions (take) place in the previous twenty years. 答案：【1】had taken自由下落的物体，自起点开始依次下落三段相等位移所用时间之比是（    ） A.1∶3∶5                              B.1∶4∶9 C.1∶∶                         D.1∶(-1)∶(-)