I'm not sure she believes me. She probably just thinks I've gone off the deep end.

　　我不確定她是不是相信我。她可能只是覺(jué)得我神志不清了。

　　I'm not sure whether I should tell you this.

　　我拿不準(zhǔn)該不該把這事告訴你。

　　I'm not sure that this is the most valuable use of my time.

　　我不能肯定我的時(shí)間這樣來(lái)安排最有價(jià)值。

　　I think this is their house, but I'm not sure.

　　我想這是他們家，但不敢肯定。

　　One should never criticize if one is not sure of one's facts.

　　一個(gè)人如果對(duì)自己掌握的事實(shí)沒(méi)有把握，就絕不該隨便批評(píng)。