There are many types of chemical reactions. Four are described below: Synthesis: Two or more reactants combine to form a single product. For example, 2H2 + O2 → 2H2O. (Synthesis reactions are also called combination reactions.)
Decomposition: One reactant breaks down to form two or more products. For example, 2KCl → 2K + Cl2.
Single replacement: An element reacts with a compound to form another element and compound. For example, Zn + 2HCl → ZnCl2 + H2.
Double replacement: Two compounds react to form two different compounds. For example, FeS + 2HCl → FeCl2 + H2S.

Identify the following examples as one of the four choices (from above). In these examples, I’m using letters (A, B, C, D etc) to represent chemical symbols more simply.
Example: X + YZ -> XZ + Y, you would say this is an example of a single replacement reaction.

ABCD -> A + CD + B

AD + CB -> AC + BD

AC + BD -> ACBD

D + EG -> DG + E

Can somebody please help me?? have a blessed day god bless!! - Natalia