What you're looking for is an equation where all the same atoms show up on both sides, although maybe in different combinations.
As an example, look at #2. It has two Oxygen atoms on the left side, and only one Oxygen atom on the right side. What happened to the other Oxygen atom ? Chemical reactions don't work that way. Atoms don't magically appear or disappear during a chemical reaction.
#1 says that 1 Sodium atom (Na), 1 Oxygen atom, and 1 Hydrogen atom all disappeared during the reaction and were never seen again.
#4 says that 1 Chlorine atom disappeared. There are 2 of them on the left side, but only 1 of them on the right side.
#3 is the only one on this list that has the same atoms on both sides of the equation.
