Chemistry · Structure of atom

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).\n Assertion (A): Copper has the outer electronic configuration of \( 3d^{10} 4s^1 \) instead of \( 3d^9 4s^2 \).\n Reason (R): Fully filled and half-filled subshells have extra stability due to high exchange energy and symmetrical distribution. \nIn the light of the above statements, choose the correct answer from the options given below:

1. A
   Both (A) and (R) are true and (R) is the correct explanation of (A).
2. B
   Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
3. C
   (A) is true but (R) is false.
4. D
   (A) is false but (R) is true.