For the given molecule, "x", the preferred site for the attack of the electrophile is :

In N-phenylbenzamide, the two benzene rings are connected through an amide linkage $$(-CO-NH-)$$.

• The benzene ring attached directly to the carbonyl carbon $$(-CO-)$$ is deactivated due to the strong electron-withdrawing $$-R$$ and $$-I$$ effects of the carbonyl group. Hence, this ring is less reactive towards electrophilic aromatic substitution.
• The benzene ring attached to the nitrogen atom $$(-NHCOPh)$$ receives electron density through resonance from the lone pair present on nitrogen. Although this lone pair is partially involved in resonance with the carbonyl group, the ring attached to nitrogen remains more electron-rich than the ring attached to the carbonyl carbon.

The $$-NHCOPh$$ group acts as an ortho/para-directing group. Therefore, electrophilic substitution occurs preferentially at the ortho and para positions of the ring attached to nitrogen.

Between the ortho and para positions:

• The ortho position ('s') experiences steric hindrance due to the bulky amide group.
• The para position ('u') is less sterically hindered and is therefore the preferred site for attack.

Hence, electrophilic substitution occurs predominantly at position 'u'.

Therefore, the correct option is (D).