How did you work out this very____physics problem last week,Liz?

问题描述:

How did you work out this very____physics problem last week,Liz?
By_______
A.easy;worked on my own B.difficulty;doing an experiment
C.hard;ask my friends for help
D.difficult; working with my deskmate
我的想法是difficult修饰problem,所以选D

同意.第一空三、四均可,但第二空by后应加状语,四中用现在分词符合要求,三中用动词原形,不能作状语.故选四D.