Aplacebo is a substance that is unlikely to affect the dependent variable.
a. true
b. false

replacement

Explanation:

There are two types of replacement reactions.

Double replacement:

It is the reaction in which two compound exchange their ions and form new compounds.

AB + CD → AD +CB

Single replacement:

It is the reaction in which one elements replace the other element in compound.

AB + C → AC + B

The given reaction is double replacement reaction because anion and cation of both reactants exchanged with each other.

Other options are incorrect because,

Decomposition reaction:

It is the reaction in which one reactant is break down into two or more product.

AB → A + B

Synthesis reaction:

It is the reaction in which two or more simple substance react to give one or more complex product.

Oxidation:

Oxidation involve the removal of electrons and oxidation state of atom of an element is increased.