For each of the following, indicate whether the expected relationship between the two variables will be positive (+), negative (-), or zero (0):
______a. Air temperature and the amount of snow on the ground
______b. The number of minutes of exercise per day and score on a physical fitness test
______c. The number of years having a driver's license and age
______d. The number of pages in a textbook and cost of that textbook
______e. Age at which a child takes its first step and educational level of the parents