例句：

　　Certain of those present were unwilling to discuss the matter further.

　　某些在場的人不愿意進一步討論這個問題。

　　Those beliefs still prevail among certain social groups.

　　這些信念在某些社會群體中仍很盛行。

　　The work must be completed within a certain time limit.

　　這項工作必須在一定期限內(nèi)完成。

　　The company's financial position is not certain.

　　這家公司的財務(wù)狀況不明朗。

　　Many animals breed only at certain times of the year.

　　很多動物只在一年的某個時候繁殖。