The correct order of the size of C, N, P and S is

C and N are of 2nd period element. Size decreases from C to N. Therefore, size of N < C.P and S are of 3rd period elements. But size of P > S [opposite to the expected trend, i.e. size of S > P].Moreover, size of 3rd period elements is greater than that of 2nd period. Hence the correct order of sizes is P>S 3rd period >C>N 2nd period