Answer:
D. The constant 250 represents the average collection when no seniors ride.
Step-by-step explanation:
A -- the entire expression represents the driver's pay, not just the constant 250.
B -- collections continue to increase as x goes up, so 250 is the minimum, not the maximum.
C -- x is the number of seniors; 250 is in units of collections (dollars?), not numbers of seniors.
D -- indeed, 250 is the "y-intercept" of the expression, hence the collection when no seniors ride.