在通常情况下，动词前面只连用一个情态动词。但 can and must 算是例外，意思是“能够且必须”：

You can and must act boldly. 你可以而且必须果敢行事。

These difficulties we can and must conquer. 这些困难我们能够也必须克服。

You can and must act boldly and confidently. 你能够而且必须表现得勇敢和自信。

For purposes of litigation, an infant can and must be represented by an adult. 为诉讼目的，婴儿可以而且必须由一位成人代表。