The correct option is A 18,32
Maximum number of electrons that can be present in M and N shells are 8,18 respectively.
M shell corresponds to n=3. So, 2n2 and total 18 electrons are possible in M shell.
N shell corresponds to n=4. It has 4s, 4p and 4d subshells. s subshell has 2 electrons, p subshell has 6 electrons and d subshell has 10 electrons. . So, 2n2 total 32 electrons are possible in N shell.