Ontario Grade 9 Science Class Practice Exam

Biomass refers to the total mass of living organisms in a given area. This includes all living things such as plants, animals, and microorganisms. Option B may be a common association with the word "biomass," but it is not a complete or accurate definition. Option C only refers to a specific type of biomass, while option D narrows the definition to just waste in an ecosystem, which does not encompass all living organisms. Therefore, option A is the most accurate and complete definition of biomass.