Many Russian interrogatives start with к-:
кто? кому? куда? кем? как? который? где? (<кде?) когда?
On the other hand, some interrogatives start with ч-. They seems to be case variants of "что?":
что? чему? чем? чего? о чём?
I suppose that all these interrogatives came from Proto-Indo-European "qu̯-", which also gave English wh- (as in what, who, when, which,...).
Yet I wonder why кто ("who") and "что"("what") got different initial consonant? Can it be explained solely by dissimilation?