她把信塞进信封并封好了。

She ___slipped the letter ___into an envelope and sealed it.

他把纸条从门缝里塞了过去。

He ___slipped the note ___through the crack in the door.

间谍偷偷地把微缩胶卷塞进了口袋。

The spy ___slipped the microfilm ___into his pocket discreetly.