The biosphere can best be defined as part of the

Step 1: Analyze the question The question asks for the best definition of the biosphere. Break the word down: "bio" means life, and "sphere" refers to a region or zone of the Earth.

Step 2: Explain the concept The biosphere is the zone of the Earth where life exists. It is made up of parts of three layers:

• Lithosphere (land and soil)
• Hydrosphere (water bodies)
• Atmosphere (the lower layer of air)

It is where living organisms interact with each other and with their physical environment. It includes forests, savannas, rivers, oceans, soil, and the lower atmosphere.

Step 3: Check each option

• A. Atmosphere that contains moisture: This covers only part of the air and says nothing about life. Wrong.
• B. Earth that contains gases: This describes the atmosphere, not the biosphere. Wrong.
• C. Earth that is liquid: This describes the hydrosphere. Wrong.
• D. Earth that supports life: This matches the definition, covering all the places where life exists. Correct.
• E. Ocean that supports life: This is too narrow. The biosphere includes land and air as well as the ocean. Wrong.

Step 4: Answer The biosphere is the part of the Earth that supports life, so the answer is D.

Exam tip: Split the word: bio = life, sphere = zone. If an option links the word to "life" in a broad way, not limited to just water or air, that is usually the answer. Also watch for options like E that are too specific. Because the biosphere spans land, water, and air, any option naming only one of them is too narrow.