Answer:
C
Explanation:
Just look at the reactants.
2AgCl + BaBr2
The first reactant is made of 2 elements.
The second reactant is made of 2 elements.
It can't be a decomposition. At this level there is only one reactant made of 2 elements. Something like
2MgO ===> 2Mg + O2
is a decomposition. One compound breaking down into 2 elements Mg and O.
It can't be a combustion. One of the reactants in a combustion is oxygen. Those equations look like
C3H8 + 5O2 ==> 3CO2 + 4H2O
That would be what a combustion looks like
It can't be a single replacement. They look like
Mg + CuO ===> Cu + MgO
There are elements on both sides of the reaction.
that leaves a double replacement which I wrote about how you distinguish it.