Which of the following sets of quantum numbers represents the highest energy of an atom?
(a) n = 3, l = 0, m = 0, s = + 12
(b) n = 3, l = 1, m = 1, s = + 12
(c) n = 3, l = 2, m = 1, s = + 12
(d) n = 4, l = 0, m = 0, s = + 12

Dear student

option c is right 

(a) n = 3, l = 0, m = 0, s = + 1/2  --->  3s
(b) n = 3, l = 1, m = 1, s = + 1/2 ----> 3p
(c) n = 3, l = 2, m = 1, s = + 1/2  ----> 3d
(d) n = 4, l = 0, m = 0, s = + 1/2   -----> 4s

According to Aufbau's principle,
The increasing order of energy among these orbitals is 3s<3p<4s<3d
∴3d has the highest energy.

Also, here (n + l) value for 3d is  highest among all as ( n + l = 3 +2 = 5).

Regards