It is necessary that the problem ______ in some way or other.
A. is settled
B. has been settled
C. be settled
D. was settled
Experiments ______that accurate measurements be made.
A. show
B. prove
C. demand
D. declare
_______________, he would have come to class.
A. If Mike is able to finish his homework
B. Would Mike be able to finish his homework
C. If Mike could finish his homework,
D. If Mike had been able to finish his homework
半加器进位输出端与输入端的逻辑关系是（ ）。
A. 与非
B. 或非
C. 与
D. 异或
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