Which liquid makes bubbles that are the largest? Which liquid makes bubbles that are the prettiest? Which liquid makes bubbles that are the best smelling? Which liquid makes bubbles that are the most interesting?
I gave my students this multiple choice question: Students are studying liquids that make bubbles. Which question could be answered by using a ruler?

Only one answer is correct among these 4 choices:
- Which liquid makes bubbles that are the largest?
- Which liquid makes bubbles that are the prettiest?
- Which liquid makes bubbles that are the best smelling?
- Which liquid makes bubbles that are the most interesting?

Could you tell me which one is correct?

Which liquid makes bubbles that are the largest?