The sum of the largest and the smallest numbers among
$$\frac{3}{4}, \frac{4}{5},\frac{2}{3},\frac{5}{6}$$ is

A

$$\frac{3}{4}$$

B

$$\frac{2}{3}$$

C

$$\frac{4}{5}$$

D

$$\frac{5}{6}$$