If the spin of one electron in an orbital is spin-up, what is the spin of the other electron in that orbital?
2 electrons can occupy an orbital, and there are only 2 possibilities to the spin.
One election can be "spin-up", this means that the other electron has to be the opposite of that, so in this case, the other would be "spin-down"
For this question, one electron is going spin-up. This means the other electron has to be the opposite, so it would be spin-down.