The mileage for a motorcycle varies directly as the amount of gas used. The motorcycle travels 300 miles on a tank of gas, and the tank holds 4 gallons of gas. About how far can the motorcyclist travel if the tank currently contains 1.5 gallons of gas?

A. about 75 miles.
B. about 112.5 miles.
C. about 150 miles.
D. about 800 miles