【问】 People travelling long distances frequently have to decide whether they would prefer to goby land，sea，or air.(New Concept English，Book 3，L. 44)

句中的副词frequently是修饰哪个成分的?是修饰travelling，还是修饰have to?

【答】 从句意上看，把frequently看作是travelling的修饰语，还是have to的修饰语都是讲得通的。但是，从语法上看，frequently只能是修饰have to的。根据英语惯用法，have to的状语要放在它的前面。例如：

We apparently have to go.(AEG)

但是，在其他情况下(即have不带to时)，状语要放在have的后面：

1. He has apparently gone. (AEG)

2. I have never mentioned it.