掘沟、剥离和采矿三者之间的何关系？
参考答案：
即相互依存又相互制约。
--- We went to see the man who was in hospital yesterday. --- __________.
A．So did we
B．So we did
C．We did so
D．Did so we
UPS输出变压器的原则边连接方式为（）
A、△-Ｙ
B、Ｙ-△
C、△-△
D、Ｙ-Ｙ
