As the electron is present in 5 th orbit in s -subshell and value of l for s -subshell =0 Values of magnetic quantum number (ms) for s -subshell can be calculated as follows: ms=−1......0+.......+l l=1,ms=−1,0,+1........ so on. Hence, value of magnetic quantum number of the electron in s -subshell is also zero. Hence, (b) is the correct option.