some of the experiments ( )in our textbook are difficult to perfo_英语解答

some of the experiments ( )in our textbook are difficult to perform.
答案给的是described,但是为什么不用be described呢?

人气：272 ℃　时间：2020-03-24 23:11:03

解答

此时described是过去分词做定语,以意被描述的.因为有了主语some of the experiments()做主语,are为谓语,所以不能再出现谓语了.