Answer:
d. n = 4, l = 2, m = 0
Explanation:
A d-orbital in the fourth energy level can only be represented by n = 4, l = 2, m = 0.
n is the principal quantum number(n) which signifies the energy level, here it is 4;
l is the azimuthal quantum number or l which signifies the shape of the subshell, it takes a value of n - 1, 0,1,2 or 3
m is the magnetic quantum number(m) which can be -2, -1, 0, 1 , 2
So, the right and fitting solution is n = 4, l = 2, m = 0
