A salesman for the telephone company Yellow Pages tells store owners that the bigger their advertisement, the more calls they will receive from potential customers. In this situation, the dependent variable is ______.

A) bigger advertisements
B) customers
C) number of calls
D) size of advertisement

The dependent variable is the variable that is being measured or observed, which is the number of calls received by the store owners. The size of the advertisement may be an independent variable, as the salesman is suggesting that it can be changed to affect the dependent variable. However, the dependent variable in this situation is the number of calls received. Therefore, C (number of calls) is the correct choice for the dependent variable.