20. $\lim x \rightarrow 0 ( x \tan 2 x - 2 x \tan x ) / ( 1 - \cos 2 x ) 2$ is:\\ (A) $y = 2$\\ (B) $y = 2 x$\\ (C) $y = 2 x - 4$\\ (D) $y = 2 \times 2 - 4$\\