if you don't mind, if you like, if you're so inclined

nothing

what number, how many (used with a counter) / (used with も) many (used with a counter)

What?, Huh?

what / that thing (used in place of words you can't remember at the moment.)

what

what is this?

let's see; what have we got here

which (of three or more) / which one /

Nothing