In the reaction
$$2X + B_2H_6 \rightarrow [BH_2(X)_2]^{+}[BH_4]^{-}$$
the amine(s) X is (are)

A

$$NH_3$$

B

$$CH_3NH_2$$

C

$$(CH_3)_2NH$$

D

$$(CH_3)_3N$$