Got 100% no problem. However, I question putting UB40 on this quiz, since 4 and 0 aren't letters. Thus, UB40 is a two-letter musical act. I recommend either making a note of that in the footnotes, changing the quiz's title to "Four-Character Musical Artists", or removing UB40 from the quiz completely.
I was going to say something about P!nk's technicality, and then I came across UB40. Maybe mention some answers contain four characters, not necessarily four letters.