单项选择题

It was only after some progress ______ in the use and development of electric current that men began to realize the importance and possibilities of magnetism.

[A] was made
[B] would have been made
[C] has been made
[D] had been made
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单项选择题
Railway workers joined in the strike because they
A．attempted to halt the whole network for train travel.
B．were dissatisfied with proposed rise in unemployment.
C．were unhappy with their working conditions.
D．wanted to Support workers from other unions.
单项选择题
When children are about four years old, they are the most
A．original.
B．vigorous.
C．curious.
D．ambitious.
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