a great deal of research has been done into the possible causes of cancer.何意?
问题描述：
a great deal of research has been done into the possible causes of cancer.何意?
答
进行大量的研究来找到癌症的致病原因。
答
句意：为了找到癌症的致病原因,人们已经做了大量的研究.
这个句子是用被动来表达的.