Answer:
D. Mortgage approval rates and housing prices
Step-by-step explanation:
From the study being conducted by the economist, the two variables in their study happens to be the Mortgage approval rates and the housing prices. This is because, the local housing market is influenced by those two.
The higher the value of one variable, it may have a direct or indirect influence on the value of the other variable. To determine the relationship between the two means it need to be investigated.