certain的副词和名词

　　例句：

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

　　某些在场的'人不愿意进一步讨论这个问题。

　　Those beliefs still prevail among certain social groups.

　　这些信念在某些社会群体中仍很盛行。

　　The work must be completed within a certain time limit.

　　这项工作必须在一定期限内完成。

　　The company's financial position is not certain.

　　这家公司的财务状况不明朗。

　　Many animals breed only at certain times of the year.

　　很多动物只在一年的某个时候繁殖。