Answer:
D. They must have opposite spins.
Step-by-step explanation:
Two electrons in the same atomic orbital have different spins or spin number. If one electron has +1/2 spin the other electron will have -1/2 spin. In other words if one electron is spinning in the clockwise direction the other electron will be spinning in the anticlockwise direction. Two electrons in the same atomic orbital have the same principal quantum number (n), azimuthal quantum number (l) and magnetic quantum number (m).