as to the specific it's/its question, i think the majority of adults whom ! i know , would not be sure about that.
the few who would are probably older people, over 75 and went to grammar school.
and maybe not all of them, if they were on the science side.
so by definition that is a minority of the populus.
someone above said it was basic. don't think i can agree with that.
when i was at school we did comprehension, and correcting passage of text that had these sort of errors. which made it more interesting. hunt the aberrant apostrophe.
nowadays children seem to have to learn reams of strange linguistic terms, which to me is pointless and off-putting.