题目

Can you tell me ________at that time?   A. Where are you                    B. Where you are  C. Where were you                  D. Where you were 答案：D如果把中的x与y都扩大为原来的5倍，那么这个代数式的值（ ）A. 不变 B. 扩大为原来的5倍 C. 扩大为原来的10倍 D. 缩小为原来的