Question

be sure to是什么意思，怎么用

Answer 1

1）意思：
一定，必须

2）用法：
be sure+不定式，表示说话人对句子主语作出的判断，认为句子主语“必定”、“必然会”、“准会”如何如何。

It is sure to rain．天一定会下雨。

He is sure to have known about that．他准会知道那件事。

He told me I was sure to get a warm welcome．他告诉我，说我准会受到热情接待的。

然而be sure to do用在祈使句中，不是表示判断，而是表示对对方的要求，意为“务必要”，“一定要”。例如：

Be sure not to forget it！千万别忘记呀！

Be sure to send my regards to your mother．务必代我问候你母亲。

Be sure not to do that again．一定不要再干那种事了。

Answer 2

一定要