Final answer:
Endothermic reactions absorb heat from the environment, while exothermic reactions release heat into the environment, causing a decrease and increase in the temperature of the surroundings, respectively.
Step-by-step explanation:
The key characteristic that distinguishes endothermic reactions from exothermic reactions is whether they absorb or release heat. Option c correctly states that endothermic reactions absorb heat from the environment.
This means that during an endothermic process, heat is taken in by the system from the surroundings, leading to a decrease in the temperature of the surroundings.
Conversely, option b describes exothermic reactions, which release heat to the environment, causing an increase in the temperature of the surroundings because the system is losing heat. In other words, in endothermic reactions, energy is required and acts as a reactant, while in exothermic reactions, energy is given off and can be considered a product.