Um what happen when you mix salt and soda?

a. it fizzes up b. it blows up or c. nothing at all

It blows up. The reason this happens is very simple: When the salt gets dissolved by the soda, it changes the balance of the soda's chemistry and forces the release of carbon dioxide bubbles from the solution. Essentially, the salt "crowds out" the carbon dioxide and replaces it in the soda. The carbon dioxide then has nowhere else to go but out, which is why it will explode out of the soda bottle.