Students are studying liquids that make bubbles. Which question could be answered by using a ruler?
A Which liquid makes bubbles that are the largest?
B Which liquid makes bubbles that are the prettiest?
C Which liquid makes bubbles that are the best smelling?
D Which liquid makes bubbles that are the most interesting?
Looks, smell, and interestingness of bubbles may not be measured by a ruler. Therefore, the answer is A. (Measuring the size of bubbles using a ruler may be difficult but not impossible.)
