When do children start asking "why?" - and other WH questions

[ItNeverRainsBut]

Do children generally learn WH questions in the same order? and are there ages by which you would expect a child to be able to answer them? If anyone can point me in the direction of any info on this that would be great!

Order - who, what, where

then why and when

then how

www.speech-language-therapy.com/devel2.htm

the above site suggestions 1-2 years to respond to simple questions like "where's the bunny" and 3-4 for responding to who/what/where questions

Thank you, that's a useful link.