Which Statement Is an Example of a Positive Correlation

Which statement is an example of a positive correlation?

A) As exercise increases, a person's physical health would be predicted to increase.
B) As immunizations increase, the rate of illnesses would be predicted to decrease.
C) As poor weather conditions decrease, the number of motorcycles on the highway would be predicted to increase.
D) As gas prices decrease, the number of people driving cars would be predicted to increase.