Two electrons in the same atom that have identical values of the quantum numbers n, l, and ml are said to be in

The four quantum numbers are n, l and ml, and ms.

The first three of them describe the orbital on which the electron of an atom is.

n is the main quantum number and it represents the shell. This is also the row (period) on the periodic table.

l is the orbital angular momentum number and it tells the shape of the orbital. It may be

0 which is s orbital

1 is p orbital

2 is d orbital

3 is f orbital

ml is the the magnetic quantum number: It gives the position of the orbital in the space.

Those three quantum numbers, n, l, and ml, then, determine the orbital.

The fourth quantum number, ms, is the spin.

the two electrons with the same n, l, and ml quantum numbers are said to be in the same orbital.

The answer is a) carbon-12