exciting sport it is to climb the mountains!A. HowB. WhatC. What a D. What an

问题补充：

exciting sport it is to climb the mountains!

A. How

B. What

C. What a

D. What an

答案：

A. How

B. What

C. What a

(答案→)D. What an

解析：句意：爬山是一件多么让人兴奋的运动。sport为单数可数名词，exciting为元音音素开头发音的单词，故选D