ABCD is a trapezium with parallel sides AB = a cm and DC = 6 cm E and F are the mid-points of the non-parallel sides. The ratio of ar (ABFE) and ar (EFCD) is

Options

A. `a:b`
B. `(3a+b):(a+3b)`
C. `(a+3b):(3a+b)`
D. `(2a+b):(3a+b)`.