"quit"后面通常接 doing，表示停止正在做的事情。例如：

1. She quit smoking because it was harmful to her health.

2. They decided to quit their jobs and start their own business.

"quit"后面也可以接"something"，但这通常指的是停止做某件事情，而不是正在做的事情。例如：

1. He quit his job as an office boy because he wanted to pursue other interests.

2. She quit her hobby of painting because it was too time-consuming.

总结：

"quit doing something"：停止正在做的事情。

"quit something"：停止做某件事情（不强调正在做）。