The accident ___ downtown yesterday resulted from the driver's carelessness.
A.happening
B.happened
C.which had happened
D.which happened
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The factory has turned out ___.
A.twice more TV sets this year than last year
B.TV sets this year twice as many as last year
C.twice as many TV sets this year as last year
D.TV sets twice more this year than last year
She waited at the gate, her hands ___ before her.
A.folding
B.folded
C.were folding
D.were folded
矩磁材料具有较 （小或大）的矫顽磁力和较 （小或大）的剩磁。
若变压器的变比为100，在二次端接5Ω的负载电阻相当于直接在一次端接Ω的电阻。
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