单项选择题

Electricity （） by the Greeks a good many years ago.

A.was first found
B.was first discovered
C.has first been discovered
D.was seen first

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单项选择题

A.trained
B.has trained
C.would trained
D.had trained

单项选择题

A.should
B.ought
C.must
D.shall

单项选择题

A.Who are you
B.What’s the problem
C.Are you Jane
D.Who’s speaking?