1. be sure肯定，确信 主要搭配有：be sure that..., be sure of/about, be sure to do等 I am sure that I put the money in the box. 我肯定把钱放在盒子里了。 He said he would come with his wife, and sure enough he did.
2. ensure vt.
(1)保证；担保[+that][+v-ing]
I can't ensure his being on time. 我不能保证他的准时。
I can't ensure that he will be there on time. 我不能担保他会及时到那儿。
This medicine will ensure you a good night's sleep. 这药将保证你一晚睡眠良好。 (2)使安全，保护[(+from/against)]
These are safety devices to ensure workers against accidents. 这些安全设施是为了保护工人不出事故。
3. assure vt.
(1)向...保证，使确信，让...放心 assure sb. that
Mom assured us that everything would be all right. 妈妈向我们保证一切都不会有问题。 assure sb. of sth
the dealer had assured me of its quality (2)be assured of 有信心，有把握
4. make sure 确定；确保 make sure of sth make sure that