题目

He's very good at English. He spends most of his free time______ new words. A. remember    B. remembering  C. remembers  D. remembered 答案：B将系于绳端质量相等的铁桶和实心铁球同时浸没在水中，静止在图中所示的位置．则绳子对它们的拉力F1和F2的大小关系是（ ）A．F1＞F2B．F1＜F2C．F1=F2D．以上三种情况都有可能