The coefficient of middle term in the expansion of $$(1 + x)^{40}$$ is

A

$$\frac{1.3.5 .... 39}{20!} 2^{20}$$

B

$$\frac{1.3.5 .... 39}{20!}$$

C

$$\frac{21.22 .... 40}{20!}$$

D

$$40! 2^{20}$$