____did he realize that he had made a mistake.
A. upon entering the classroom
B. only after entering the classroom
C. after he had entered the classroom
D. as soon as he entered the classroom
____ a machine been so efficient and accurate as the electronic computer.
A. more than ever before
B. never before has
C. in the past, there never has
D. formerly there never was
little ____ about him when i first met him in that company.
A. have i known
B. had i known
C. do i know
D. did i know
at no time, and under no circumstances ____ the first to use nuclear weapon.
A. china will be
B. will be china
C. will china be
D. shall china be
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