问题
选择题
Personal computers _______ in 1976. It has changed the whole world. [ ]
A. have been invented
B. are invented
C. were invented
D. invented
答案
答案：C
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Personal computers _______ in 1976. It has changed the whole world. [ ]
A. have been invented
B. are invented
C. were invented
D. invented
答案：C