Here's what I got.
The model illustrated there represents the Law of Mass Conservation, which states that matter can neither be created, nor destroyed during a chemical reaction.
What that tells you is that in any chemical reaction, the total mass associated with the reactants must be equal to the total mass associated with the products.
In other words, every atom that takes a part in a chemical reaction on the reactants' side must be accounted for on the products' side.
In your case, the reactants' side contains
- one large atom
- two small atoms bonded together
Notice that the products' side contains the exact same number of atoms, one large atom and two small atoms, only this time they are all part of the same molecule.
That is perfectly fine! As long as the number of atoms balances out, you can say that you're dealing with a possible chemical reaction.
SIDE NOTE To be perfectly honest, I have no idea what the other options are supposed to represent, at least not written in that form.
This is not a problem because in this context the model represents conservation of mass.