当要求几个条件同时具备时，电器线圈才能通电动作，可用（）。

A.几个动合触头与线圈并联

B.几个动合触头与线圈串联

C.几个动合触头并联再与线圈串联

D.几个动合触头串联再与线圈并联

.

Mary had to work at evenings and weekends. Only in this way _____ complete the reports by the deadline.

A．was she able to

B．she was able to

C．she has been able to

D．has she been able to