Underlined carbon is $sp^3$ hybridised in :

Question

( A ) $CH_3 \underline{C}H_2 NH_2$
( B ) $CH_3 \underline{C}H = CH_2$
( C ) $CH_3CH_2 \underline{C}N$
( D ) $CH_3 \underline{C}O NH_2$