Carbon Cycling Provides Essential Building Blocks for Life

Steps:

• Carbon forms the backbone of organic molecules like proteins, carbohydrates, and lipids essential for all life.
• The carbon cycle recycles carbon through processes like photosynthesis, respiration, and decomposition to maintain availability.
• Without cycling, carbon would become locked in unavailable forms, halting growth and reproduction.
• Organisms rely on these carbon compounds to build new cells and tissues.

Why C is correct:

• Carbon is a fundamental element in amino acids, the building blocks of proteins, which all organisms need for structure and function (per organic chemistry definitions of biomolecules).

Why the others are wrong:

• A: Animals require oxygen for respiration to release energy; CO2 is a waste product they exhale.
• B: Respiration consumes carbon compounds to produce energy and CO2, not new carbon compounds.
• D: Trees absorb more CO2 via photosynthesis than they release in respiration, acting as net carbon sinks.

Final answer: C