16318616165161616156165161961616
Answer:
it's a precipitation reaction.
Explanation:
since a solid is produced, one of the elements are insoluble with one another–making a precipitate.
Among the choices, the polyatomic ion is only the third choice, NH4+ where it is composed of nitrogen one atom of nitrogen and 4 atoms of hydrogen. Choice 2 is a monoatomic atom being composed only of calcium. Then, the first and fourth choices are not ions because they are not charged.