Section Ⅳ Grammar & Writing
动词ing形式作状语
阅读下列句子，体会黑体部分的用法
1．Will, still watching, saw the cat behave curiously.
2．When it had gone past he crossed the road, keeping his eyes on the spot where the cat had been investigating.
3．While sitting by a pool, Ferdinand sees a frog.
4．Before leaving his kingdom, he calls his son to him.
