DK-1型制动机（电空位操作）“大闸”置过充位时（）线得电。
A、803、809
B、803、805
C、807、806
D、806、808
参考答案：B
A．(A) When we are attending an English language course.
B．(B) When we are watching an interesting TV program.
C．(C) When we are enjoying the murmuring of a brook.
D．(D) When we are listening for a friend’s voice in a crowd.
文法等价的定义是什么？
