A . the number of atoms in 11.2 L of O2 at STP.

B . the number of atoms in 1 mole of He at STP.

C . the number of electrons in 96,500 coulombs.

D . the number of ions in 1 L of 1 N sulfuric acid.

the correct answer is D.

But, I don't understand the reason stated on my answer key. Can anyone elaborate on the reason behind choosing D. Thanks !