sure与certain的用法区别详解
（1）be sure of和be sure about.
be sure of(表示“对…..很确信/有把握”)和be sure about(表示“一定会干某事”)后面跟“连接词（疑问词、连词whether）+不定式”结构，意思是“确定……”.
例如：I’m not sure whether to go to the party. 去不去参加聚会我还不能确定.
（2）be certain.
①和of（有时用about）连用，后接名词或动名词（用about时不跟动名词），意思是“确信”，只能用人作主语.如：He was too certain of her coming to send for her. 他相信她肯定要来，所以没有打发人去请她.
②后接从句，意思是“确信……，确定……”，只能用人作主语.
例如：I’m certain (that) he saw me.我确信他看见了我.
③后面跟“连接词（疑问词、连词whether）+不定式”结构，意思是“确定……”，只能用人作主语.
例如：They were not certain whether to go or not. 他们不能确定该不该去.
④表示“（某人做某事）肯定无疑的”时，要用It is certain that …句型（该句型中不能用sure, It is certain for sb. to do sth. 这样的用法是错误的.）
例如：It is certain that your team will win. 你们队肯定会赢.
[注意]这一句型可以转换为：Your team is certain to win. / Your team will certainly win.
1. Wait till you are more         .It’s better to be sure than sorry.
A. inspired      B. satisfied      C. calm        D. certain
解：答案选D.本题考查形容词的意义辨析.从下句的It’s better to be sure than sorry. 可以判断，此处应选certain,，句意为“等到你更确信，弄确定（不出错）比（没弄确定而出错）向别人道歉更好些”.其他选项不合句意.
2. Quite a few people used to believe that disaster          if a mirror was broken.
A. was sure of striking     B. was sure of having struck
C. was sure to be struck    D. was sure to strike
解：答案选D. be sure of doing 表示“对…..很确信/有把握”；而be sure to do表示“一定会干某事”；而strike可作为不及物动词使用，表示“降临”，本句意思为：“过去许多人相信如果镜子了，灾难一定会降临”.