不是NN,给点看法.
一般来说比较的两个主语在时间上是一致时,如须补足动词,补出与主句谓语相对应的助动词或动词即可.如果是情态动词当然也要对应情态动词.但语言是活的,当比较的两个主体在时间上不一致时,补出的谓语在时态上就要作相应的变化.
举例说明: You have more money than she has. vs. You have more money than your parents had when they were your age. 希望这些即兴例子没举错,但大概意思理解就行.
同理,当比较的两个主体在比较的语气上有变化时,后面须补出的助动词也要有所变化.比如提到的例子:
2.The guiding principals of the tax plan released by the Treasury Department could have even greater significance for the economy than have the particulars of the plan.
用could表示the particulars of the plan的影响是猜测的,用do表示其影响已然确定.总之要看上下文的含义.
hopefully can help. | 
