The subject of these lectures ____by the lecture committee.

问题描述:

The subject of these lectures ____by the lecture committee.
A) is announced
  B) have been announced
  C) are announced
  D) has been announced
我没有看到明显的现在完成时态的时间词啊.

选C ,句子没有谓语动词,需要被动.你错了。不好意思,当时看的比较匆忙,没有看清楚,这样,用排除法。首先句子主语是单数,谓语动词显然只有AD适合,而A显然不适合。句子D翻译为这个讲座的主题已经被讲座委员会宣布了。