__________, many problems of space flight could not be solved now.
A. If electric computers would not have been invented
B. Had electric computers not invented
C. Had electric computers not been invented
D. If electric computers were not invented
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Busy ___he is ,he can fulfill the task ahead of the schedule.
A. because
B. as
C. no matter how
D. although
Only in the way______solve the problem.
A. we can
B. can we
C. would we
D. wewould
Never__to the U.S.A..
A. I have been
B. do l have
C. have I been
D. have l do
Do you know John always quarreled with his mother? I don't know_______
A. nor don't I care
B. l don't care neither
C. nor do I care
D. I don't care also
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