# The bond dissociation energies of $X_2, Y_2$ and $XY$ are in the ratio of 1 : 0.5 : 1. $\Delta H$ for the formation of $XY$ is $-200\; kJ \;mol^{-1}$. The bond dissociation energy of $X_2$ will be :
( A ) $200\; kJ\; mol^{-1}$
( B ) $100\; kJ\; mol^{-1}$
( C ) $800\; kJ\; mol^{-1}$
( D ) $400\; kJ\; mol^{-1}$