In $CH_3 − CH_2 − CH_2 − Br$, $C-Br$ bond is formed by the overlapping of

Question

$\begin {array} {1 1} (A)\;sp^3-2pz & \quad (B)\;2sp^3-3pz \\ (C)\;2sp^3-2pz & \quad (D)\;2sp^3-4pz \end {array}$