有一读者来信问：在《英语语法手册》一书中列举了疑问代词 who, what, which 和疑问副词 when, where, how, why 等可后加动词不定式。但查阅了许多词典和语法书， 皆不见 why 加动词不定式结构，请问疑问副词 why 到底可不可以后接动词不定式？
有不少读者提出过这个问题。一般说来，疑问副词 why 后是不加带 to 的动词不定式的,但偶尔也有例外，如：
(1)I'm wondering why to go at all.
why 虽不可后接带 to 的不定式，但可后接不带 to 的不定式，如：
(2)Why leave the door open?
(3)Why turn off the light?
(4)Why argue with him? He'll never change his mind.
再请看 “why not + 不带 to 的不定式”结构：
(5)Why not try again?
(6)Why not tell him so?
(7)— My girlfriend's in a bad mood.
— Why not give her some flowers?
