— We believe Jack can pass his exam this time.
— Yes, I agree. he works in his free time!
A. What hard
B. How hard
C. How hardly
D. What a hard
网友回答
A. What hard
(答案→)B. How hard
C. How hardly
D. What a hard
解析：感叹句主要有what和how构成：
1、what修饰名词或名词短语，有以下两种形式： 1. What+a(an)+（形容词）+单数可数名词+主语+谓语！或是：What+名词词组+主语+谓语！ 2. What+(形容词）+可数名词复数或不可数名词+主语+谓语！
2、How引导的感叹句。 how用来修饰形容词、副词或动词。其结构是：How+形容词（副词）+主语+谓语！
联系下文可知选ACD结构有误，故选B。