Ontario Grade 9 Science Practice Exam 2026 – Complete Study Resource

The biosphere refers to all living organisms and their environments on Earth. Option A is incorrect because it only includes ecosystems and living organisms in the sea, excluding those on land. Option B is incorrect because it only includes terrestrial ecosystems and organisms, excluding those in other environments like water and the atmosphere. Option D is incorrect because the biosphere includes all living things, not just the upper layer of the Earth's mantle. Option C is the most comprehensive and accurate answer as it encompasses all life on Earth and all parts of the Earth in which life exists.