1.a an
2./
3./
以上均为感叹句,句式是：What a/an +n.(c可数名词单数) (+it is/ this is /was-----可加可不加)!如题1
What + n.(c pl 可数名词复数) (+they are/were)!如题2 （we have made in the past years）为修饰 achievements 的定语,可忽略不看.
What + n.(uc不可数名词).如题3.结构用第二点一样.fun 乐趣,是uc
还有how的用法,要与what作对比.