. when the boulders suddenly disappeared.
A. So relieved we felt
B. How relieved we felt
C. What a relief we were feeling
D. How we felt relieved
网友回答
A. So relieved we felt
(答案→)B. How relieved we felt
C. What a relief we were feeling
D. How we felt relieved
解析：考查感叹句。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！ 由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！句意：当结石突然消失时，我们感到多么放松啊!结合语境可知本句叙述的是我们过去的状态，故用过去时态，so不能用于感叹句，选项D结构错误，故选B。