她把信快速塞进信封并封好。

She ___slipped the letter ___into an envelope and sealed it.

他把纸条从门缝里快速塞过去。

He ___slipped the note ___through the gap in the door.

间谍神不知鬼不觉地把微缩胶片塞进口袋。

The spy ___slipped the microfilm ___into his pocket unnoticed.