演员们不得不在没有剧本的情况下即兴表演。

The actors had to ___improvise their performance without a script.

露营时我们忘记带帐篷，只好临时用树枝和防水布搭了个遮蔽处。

We forgot the tent while camping, so we had to ___improvise a shelter with branches and a tarp.