Which type of reaction is respiration?

Respiration is a biochemical process in which organisms release energy byu breaking down of complex molecules. It is a type of Oxidation reaction. Oxidation because glucose is broken down and energy is released during the process.

While other options are:

Combination reaction: When two or more reactants reacts to form a single product.

Reduction: When electrons are gained then reduction takes places.

Endothermic Reaction: Reaction which absorbs heat from surrounding.