Here it says which of the following is not a valid magnetic quantum number for the seven F set of orbitals. So remember here, in order to find our magnetic quantum number values which are Ml, They're based on our L value here. Remember L can be 0, 1, 2, 3 based on the sublevel or subshell letter.
Since the letter here is F, that means L is equal to 3. Since L is equal to three Ml which is the range of it would equal -3 to +3 and all the numbers in between. So these would be all the allowable values for A7F set of orbitals.
The only one that's left out is +4. This would mean that D would be our correct answer. This one should not be one of the valid values for Ml when given a set of seven F orbitals.