The correct option is D 1s2,2s2,2p6,3s1
Consider the configurations of the options after the loss of an electron:-
A) 1s2,2s2,2p6
B) 1s2,2s2,2p6,3s1
C) 1s2,2s2
D) 1s2,2s2,2p6,3s2,3p2
The difference between IE1 and IE2 will be maximum for the case where there is a fully filled orbital. In this case, option A has attained noble gas configuration after the loss of an electron. Hence option A has the maximum difference between IE1 and IE2.