A chemical reaction is defined as the reaction in which bonds between the reactants either break or form which leads to the formation of a new substance.
For example,
So, when we drop a sodium metal into water then it produces a frizzing sound which shows the metal is reacting with water.
We know that when two aqueous solutions chemically react with each other then it may lead to the formation of an insoluble substance which is known as precipitate.
This means that formation of a precipitate is also a chemical reaction.
Thus, we can conclude that following are the statements which show evidence for a chemical reaction.
Dropping sodium metal into water produces fizzing.
Mixing two aqueous solutions produces a precipitate.
Neutralization is the probable answer, which I don't know how to explain, but I know that's the answer because I learned about it a few years ago and I'm pretty smart. =]