Which ratio is incorrectly written in Olivia's conversion?

Choice 3

Step-by-step explanation:

The third fraction (third refers to the answer number) is incorrect. As written, the cups won't cancel. The correct way to do this is to invert the fraction.

4 tablespoons

1/4 cup

This is an extremely important procedure to know. Make sure you understand what the basis of it is. Often  times in higher physics, you don't have a proper relationships and this method (called dimensional analysis) is the only tool you have to work with.

So each term has at least 1 cancelation that occurs with the prior term. And it is the units that you look to cancel, and that determines which way to put the intermediate steps.