What are the possible values of n and ml for an electron in a 5d orbital ? A) n = 5 and ml = -2, -1, 0, +1, or +2 B) n = 1, 2, 3, 4, or 5 and ml = 2 C) n = 5 and ml = 2 D) n = 1, 2, 3, 4, or 5 and ml = -2, -1, 0, +1, or +2

The answer is A).
The principal quantum number, or ##n##, describes the energy lelvel in which the electron can be found, Since you’re interested in an electron located in a 5d-orbital, ##n=5##.
The angular momentum quantum number, or ##l##, describes the subshell, or orbital type, in which your electron is located. Since you have a d-orbital, ##l=2##.
The value of ##l## will give you the value of the magnetic quantum number, or ##m_l##, which describes the orientation of the orbital.
The accepted values for ##m_l## range from ##-l## to ##+l##, which means that you can have 5 d-orbitals in the fifth energy level, ##d_(xy)##, ##d_(xz)##, ##d_(yz)##, ##d_(z^2)##, and ##d_(x^2-y^2)##, each described by a magnetic quantum number
##m_l = -2##
##m_l = -1##
##m_l = 0##
##m_l = +1##
##m_l = +2##
As an example, here’s how these orbitals would look for the 3d subshell