英语,用词的适当形式填空.Asresearchtechniquesbecomemoreadvanced,thenumberofanimals(use)inexperimentsmaydecrease.我觉得应该是beused啊.答案是used.为什么?如果是定语从句省略,那么到底是whichisused

Question

英语,用词的适当形式填空.
As research techniques become more advanced,the number of animals
_______(use)in experiments may decrease.
我觉得应该是be used啊.答案是used.为什么?
如果是定语从句省略,那么到底是which is used 还是which are used

Answer 1

答案是used.
表示被用于试验.used in在这里是形容animals的,如果用be used in的话,应该是：number of animals （which are）used
_______(use)in experiments
animals是复数,应该是are