Answer:
D. All of the above are true.
Step-by-step explanation:
All the given options in the problem are true.
According to Aufbau's principle, the sublevels with lower energy are filled before those with higher energies.
The order of filling according to their energies is;
1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p
We see that the 3d energy level is lower than 4f but higher than 2s.
Also, the 3d orbital has 5 subshells and each can hold a maximum of two electrons.
This gives a capacity of 10 electrons.