sure與certain的用法區別詳解
（1）be sure of和be sure about.
be sure of(表示“對…..很確信/有把握”)和be sure about(表示“一定會干某事”)后面跟“連接詞（疑問詞、連詞whether）+不定式”結構，意思是“確定……”.
例如：I’m not sure whether to go to the party. 去不去參加聚會我還不能確定.
（2）be certain.
①和of（有時用about）連用，后接名詞或動名詞（用about時不跟動名詞），意思是“確信”，只能用人作主語.如：He was too certain of her coming to send for her. 他相信她肯定要來，所以沒有打發人去請她.
②后接從句，意思是“確信……，確定……”，只能用人作主語.
例如：I’m certain (that) he saw me.我確信他看見了我.
③后面跟“連接詞（疑問詞、連詞whether）+不定式”結構，意思是“確定……”，只能用人作主語.
例如：They were not certain whether to go or not. 他們不能確定該不該去.
④表示“（某人做某事）肯定無疑的”時，要用It is certain that …句型（該句型中不能用sure, It is certain for sb. to do sth. 這樣的用法是錯誤的.）
例如：It is certain that your team will win. 你們隊肯定會贏.
[注意]這一句型可以轉換為：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：答案選D.本題考查形容詞的意義辨析.從下句的It’s better to be sure than sorry. 可以判斷，此處應選certain,，句意為“等到你更確信，弄確定（不出錯）比（沒弄確定而出錯）向別人道歉更好些”.其他選項不合句意.
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：答案選D. be sure of doing 表示“對…..很確信/有把握”；而be sure to do表示“一定會干某事”；而strike可作為不及物動詞使用，表示“降臨”，本句意思為：“過去許多人相信如果鏡子了，災難一定會降臨”.