be sure of

基本解释

We have to be sure of that first.
我们得确信这是第一位的。
“You can be sure of one thing: I’m leaving,” he says, adding that he has no plans to run for election in 2014.
“有一件事是肯定的：我要离开了，”他说道，同时还表示他并没有计划参加2014年的竞选。
All they can be sure of is that colleges will accept or reject them, and it's like being accepted or rejected for a date—only much more intense, and their parents know all the details.
他们惟一确信的，就是大学可能接受也可能拒绝他们，就像约会可能被接受或拒绝一样——只不过前者更严重一些，而且父母会知道有关的一切细节。
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He could not be sure of their support if he declared that the purpose of the war was to free the slaves.
So, he started asking himself the question, "What can I be sure of?"
他首先问自己一个问题,"我究竟能够确信什么呢"
耶鲁公开课 - 心理学导论课程节选
But I'm sure you can easily see how these styrofoam balls could, in fact, be a mono layer of gold nuclei.
这个实验怎么工作的,我们先来做些计算，但我相信你们都已经。
麻省理工公开课 - 化学原理课程节选

Although now plainly well placed to win the presidency, the Colonel cannot be sure of it.
ECONOMIST: The colonel rides on