Areaction occurs when a substance is broken down into two or more simpler substances in a chemical reaction.

The reaction is called decomposition reaction in which substance(reactant) breaks down into 2 or more substances (products).

Alinear relationship would look like a straight line on the graph. it could have a positive negative or 0 slope. so it could be a line potentially going in any direction but it must be perfectly straight.

The answer is a) taiga because taigas are cold