Equivalent circuit of FET is shown in the figure below,
where $$r_s = 100 Ω, C_{gs} = 0.1 pF$$ and $$g_m = 0.1 mho$$. For load resistance $$r_L = 500 Ω$$, the voltage gain at 1 GHz is:

A

50

B

30

C

20

D

100