The correct electronic configuration of Cu is:

Correct option is D

The correct electronic configuration of copper (Cu) is (d) [Ar]3d¹⁰4s¹
Copper is an exception to the usual order of filling electron orbitals. Instead of fully occupying the 4s orbital before the 3d, copper prefers to have a filled 3d subshell (3d¹⁰) and a partially filled 4s subshell (4s¹). This configuration is more stable due to the fully filled d subshell.