题目内容：

they are wondering __to improve their english
A if they should do B what they should C how should they do D how they should do
请各项说明理由
B 是what they should do

优质解答

they are wondering __to improve their english
D how they should do

追问：

B

追答：

句子意思是：他们疑惑该怎么做来提高他们的英语。B what they should do 语序是对的，意思是 该做什么 ； D how they should do 意思是 该怎么做 选B 强调 做什么事，采取什么措施。 可能根据上下文，选择B吧 其实 D也对的