The ion that has the same e- arrangement as ar:

a k+
b cl-
c s2-
d ca2+
e all of these

the answer is E- all of these

to check if these ions have the same e- configuration, check them in the periodic table and see where they land when you take or add electrons. 

for example, K is one space away to be like Ar, which is just one space behind. having a positive charge +1, means that it has one less electron. if you remove this electron, it is like Ar because is one space.

another example-> S-2  means you have add two electrons because charge is negative, so you add. two spaces after S land in Ar. so it is same e- configuration as Ar.

Because electrons have negligible mass, to account for the mass of the isotope, there must be 16 neutrons, 16 neutrally charged, massive, fundamental particles present in the sulfur nucleus. and thus finally, if we have the 32s2− ion, there are 18 electrons, 16 protons, and 16 neutrons.