现在分词作状语的语法功能(1作时间状语
When walking down(=When I was walking down) the street,l came across David.
沿街散步时，我偶然遇到了大卫。
When chatting with her(=When I was chatting with her), Ifound she had a gift for art.
聊天时，我发现她很有艺术天赋。