Final answer:
The variables (a) speed of an airplane, (b) age of a college professor chosen at random, (d) weight of a football player chosen at random, and (e) number of lightning strikes in rocky mountain national park on a given day are continuous variables. The variable (c) number of books in the college bookstore is a discrete variable.
Step-by-step explanation:
The variables (a) speed of an airplane, (b) age of a college professor chosen at random, (d) weight of a football player chosen at random, and (e) number of lightning strikes in rocky mountain national park on a given day are continuous variables.
Continuous variables can take on any value within a certain range. For example, the speed of an airplane can be any value between 0 and the maximum speed of the airplane. Similarly, the age of a college professor can be any positive number. The weight of a football player can vary within a certain range, and the number of lightning strikes in a national park can be any non-negative number.
The variable (c) number of books in the college bookstore is a discrete variable. Discrete variables can only take on specific, separate values. In this case, the number of books can only be a whole number, such as 0, 1, 2, etc.