Step 1 - The possible quantum numbers for a 4d electron
For a 4d orbital, the principal quantum number n would be 4 and l would be 2 (s = 0, p = 1, d = 2, f = 3, and so on).
Since ml ranges from -l to l, the possible values for ml would -2, -1, 0, 1 and 2.
Step 2 - Answering the exercise
What are most likely the values of the quantum numbers / and m/ for an
electron in a 4d orbital?
Answer: A) 2; ml -2, -1, 0, 1, 2