3. fall ill 生病 eg: The students fall ill when the flu breaks out. 流感爆发时同学们都生病了。 拓展: fall asleep 入睡; fall off 掉下;跌落; fall for 爱上;迷恋;上当;受骗; fall behind 落后 fall down 摔倒 fall to pieces 崩溃 fall in love 爱上