Babies often fall down when they are learning to walk.

　　小兒學步時常會跌交。

　　There's nothing to be afraid of. The sky won't fall down.

　　沒有什么好怕的.，天不會塌下來。

　　You are likely to fall down on your research project if you don't go to the experts for advice.

　　如果你不去向專家們請教，你的研究項目很可能夭折。

　　She didn't want to fall down like other leaves.

　　她不想像其他樹葉一樣落下。

　　She saw the leaves fall down.

　　她看到樹葉飄落。