The average snow base at Heavenly Ski Resort is 2 feet in the month of December. In the month of January, the average base is 3 feet. If the snow base increases at about the same rate through the month of March, which is the best estimate for the snow base in the month of March?

A. 2 ft
B. 3 ft.
C. 4 ft.
D. 5 ft.