A source produces 4 symbols with probabilities $$\frac{1}{2},\frac{1}{4},\frac{1}{8},\frac{1}{8}$$ For this source, a practical coding scheme has an average codeword length of 2 bits/symbol. The efficiency of the code is

A

1

B

$$\frac{7}{8}$$

C

$$\frac{1}{2}$$

D

$$\frac{1}{4}$$