问题补充：
it is to jump into a pool or go swimming in a river in summer!
A. What great fun
B. What a great fun
C. How great fun
D. How a great fun
答案：
(答案→)A. What great fun
B. What a great fun
C. How great fun
D. How a great fun
解析：考查感叹句。本题考查what + (a/an) + adj. + n. + 主语 + 谓语，fun作名词为不可数名词，选A。
