we must save the trees and not buy things made of ivory.中的“ buy things made of ivory”是一个含实义动词的句子,ok?变否定句需要借助助动词don't,ok?
问题描述：
we must save the trees and not buy things made of ivory.中的“ buy things made of ivory”是一个含实义动词的句子,ok?变否定句需要借助助动词don't,ok?但现在只有一个not,do呢?
答
首先,这是and连接的两个谓语部分在时态和语态上要保持一致；再看前一个句子we must save……（情态动词must）,and后一句话完整的否定句应该是we must not buy……,为了避免重复简洁美观,就成了你看到的这个句子啦