By the time I finished my homework,my mother .
A:slept
B:has been asleep
C:was asleep
D:had been asleep
若△ABC∽△A′B′C′,AB=2,BC=3,A′B′=1,则B′C′等于( )
数一数,有多少只 ?
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这一篇文章的核心是什么?它和《居里夫人和一克镭》有什么不同?