What is defined as the chemical decomposition of a solid material by heating?

The correct choice is B, which refers to pyrolysis. Pyrolysis is a process that involves the thermal decomposition of materials at elevated temperatures in an inert atmosphere, which typically means in the absence of oxygen. This process breaks down organic materials, such as wood, plastic, and other hydrocarbons, into gases, liquids, and char, through the application of heat alone.

Pyrolysis is significant in various applications, including waste management and energy production, as it allows for the recovery of energy from solid materials without the complete combustion that would release more pollutants. The definition aligns specifically with the question's description of the chemical decomposition of a solid material through heating.

The other terms are related to heat and chemical processes but have different meanings. Combustion involves the rapid reaction of a material with oxygen, resulting in fire and the release of gases and heat. Condensation is a physical process where a gas transitions into a liquid, often due to temperature changes. Incineration is a waste treatment process involving combustion at high temperatures, which generally destroys organic substances and results in ash and gas but is not exclusive to the thermal decomposition process described in the question.