Plz help I don’t know

1. H2 + Cl2 → 2HCl                          Synthesis

2. Ca + Br2 → CaBr2                       Synthesis

3. BaO + H2O →Ba(OH)                  Synthesis

4. 2HgO (s) --> 2Hg (s) + O2 (g)    Decomposition

5.  2 Cu + CI2 --> 2CuCI                 Synthesis

Explanation:

A synthesis reaction is a reaction in which two or more reactants combine to form a more complex substance. This reaction is often represented as: A + B --> AB.

A decomposition reaction is a reaction in which a more complex substance is broken down into two or more smaller substances. This reaction is often represented as: AB --> A + B.

I hope this help with the rest!

the correct answer to this question is 2