求NN解答一个助动词省略的问题

holly12345

曼哈顿语法中关于助动词的省略给了一个例子：
正确：I have never seen an aardvark, but last year my father saw one.
错误：I have never seen an aardvark, but last year my father did.
错误原因是如果转换时态，就不能省略。省略需要时态上的一致。


但是有两道SC PREP的正确选项就是：
#1. Since 1990 the global economy has grown more than it did during the 10,000 years from the beginning of agriculture to 1950.
#2. In the United States, trade unions encountered far more intense opposition in their struggle for social legitimacy than did the organized labor movements of most other democratic nations.
从这两道题来看，时态上并不一致，照样省略了啊。


有木有牛牛帮助解释一下这个矛盾啊？谢谢！祝杀G成功~~

hohobinger

顶一下 我也不明白 有NN能解答一下吗