Answer:
Number of feet in a mile
Step-by-step explanation:
In this problem, we need to find an option that to be created as a constant variable.
In option (a) "number of feet in a mile".
As 1 mile = 5280 foot
The number of feet in a mile is constant in every condition.
In option (b), (c) and (d)
number of people inside a store , current grade in a class , score in a football game are no fixed. It is not created as a constant variable.
Hence, the correct option is (a).