A $4$ bit $2’s$ complement representation of a number is $X_3X_2X_1X_0$. To represent it in $8$ bit form just simply copy the sign bit for an extra bit that is :
$X_3X_2X_1X_0$ can be represent in $8$ bit form as: $X_3X_3X_3X_3X_3X_2X_1X_0$.
Option (A),(B) is wrong here it represents positive and negative numbers respectively.
Option (C) is correct.