题目

It was a matter of _____ would take the position. A. who                  B. whoever            C. whom               D. whomever 答案：B某人在一星球上以速率v竖直上抛一物体，经过时间t落回手中，已知该星球半径为R，若使物体不落回该星球，则物体的发射速度至少为_________．