The maximum number of electrons in a single d sub shell is:
a) 2
b) 8
c) 4
d) 10
e) 6

No matter the nature of the orbital, it contains two electrons. Therefore the maximum electron content of a subshell is purely determined by the number of orbitals within it.

Each d subshell contains 5 d orbitals. Therefore 5*2 = 10 electrons. Therefore the answer is D.

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