由于客房不够，旅行团的成员们只能两人合住一间。

Due to limited rooms, the tour group members had to ___double-up in pairs.

在这部电影中，他一人分饰两角，既是父亲又是儿子。

In this movie, he ___doubles up as both the father and the son.

听到这个笑话，她笑得直不起腰来。

She ___doubled over with laughter after hearing the joke.