tain为后缀的单词有：
captain n.陆军上尉；队长；
certain a.确实的；肯定的；
chieftain n. 酋长,首领；
contain vt.包含，容纳；等于；
curtain n.(窗、门)帘；幕
To my certain knowledge he was somewhere else at the time.
我敢肯定他当时在别处。
I'm not certain who was there.
我无法确定谁当时在场。
As things stand at present, he seems certain to win.
据目前情况看，他似乎胜券在握。
I can't say for certain when we'll arrive.
我说不准我们什么时候能到。
It can be seen that certain groups are more at risk than others.
看得出，有的组风险大，有的组风险小。
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