题目

在板块的交界处,两个板块发生,常常形成裂谷或海洋;两个板块发生,在陆地常常形成山脉。 答案：【1】张裂【2】碰撞Most US Citizens retire around the age of 62, ____ is the national minimum retirement age. [     ]A. when      B. which           C. it              D. that