'To be'是英语中最基本的不定式。

'To be' is the most basic ___infinitive in English.

在'I want to leave'中，'leave'是一个不定式。

In 'I want to leave', 'leave' is an ___infinitive.

在'can'后面你需要使用不定式。

You need to use the ___infinitive after 'can'.