建站客服QQ：88888888 {jz:field.toptypename/} （必须/高频用 -ing 的情况） 1) 介词后面 ✅ 介 + doing - in / on / at / for / about / of / by / after / before / without / through + doing例：​- I’m good at swimming.​- After finishing work, I went home.​- He left without saying