成矿作用是指地壳中的有用组分和其余成分分离，在局部富集形成矿床的地质作用。
参考答案：对
—What happened to your classmate Jane?
—She _____ the bicycle when she practiced it yesterday and _____ her leg and arm. [ ]
A. fall down, hurt
B. fell down, was hurt
C. fell off, hurt
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