The correct option is A 10
∙ For the d-subshell, the value of l = 2. Hence, the possible values of magnetic quantum no. are -2, -1, 0 1, 2 (-l to l).
∙ Thus, d-subshell have five orbitals. Each of these orbitals can accommodate maximum of 2 electrons with opposite spins.
∙ Therefore, the d-subshell can accommodate maximum of ten electrons.