Answer: The correct option is C)
.
Explanation: The given ions are ammonium ion with +1 charge and sulfite ion with -2 charge. When the ions combined to form a compound then over all charge becomes. The over all charge becomes zero only if the positive charge equals to the negative charge.
As the ammonium ion has +1 charge and the sulfite ion has -2 charge, two ammonium ions are required for each sulfite ion. Since two ions of ammonium ion are required for each sulfite ion, the subscript of ammonium ion will be 2 and that of sulfite ion is 1. If the subscript is 1 then its not written.
Hence, the compound formula will be
and the correct option is C.