In the global carbon cycle, which natural process removes carbon dioxide from the atmosphere and incorporates it into organic molecules?

Introduction / Context:
Carbon dioxide is a key greenhouse gas and part of the global carbon cycle. Some processes release carbon dioxide into the atmosphere, while others remove it and store carbon in organic matter. This question asks which process specifically removes carbon dioxide from the air and converts it into organic compounds.

Given Data / Assumptions:
- Processes listed include combustion, photosynthesis, and respiration.
- The question focuses on removal of carbon dioxide from the atmosphere.
- We assume standard school level definitions of these processes.

Concept / Approach:
Photosynthesis is the process by which green plants, algae, and some bacteria use light energy to convert carbon dioxide and water into sugars and oxygen. Therefore, photosynthesis takes carbon dioxide out of the atmosphere and stores carbon in organic molecules. Combustion and respiration do the opposite: they break down organic molecules and release carbon dioxide back into the atmosphere.

Step-by-Step Solution:
Step 1: Recall the basic photosynthesis equation: carbon dioxide + water, using light energy, produce sugar and oxygen. Step 2: Note that carbon dioxide is a reactant in photosynthesis and is consumed during the process. Step 3: Remember that in respiration, organisms break down sugars with oxygen to release carbon dioxide, water, and energy. Step 4: Recognize that combustion of fossil fuels or biomass also breaks down carbon rich materials to release carbon dioxide. Step 5: Conclude that only photosynthesis is a net removal process for atmospheric carbon dioxide in this list.

Verification / Alternative check:
Diagrams of the carbon cycle show arrows from the atmosphere into plants labelled photosynthesis, and arrows from plants, animals, and human activities back to the atmosphere labelled respiration and combustion. The direction of these arrows confirms that photosynthesis removes carbon dioxide, while respiration and combustion add it.

Why Other Options Are Wrong:
Option A: Combustion uses oxygen and releases carbon dioxide from fuels into the atmosphere, so it adds carbon dioxide rather than removing it.
Option C: Respiration converts organic molecules back into carbon dioxide and water, so it is also a source of atmospheric carbon dioxide.
Option D: Saying that all of the above remove carbon dioxide is incorrect because only photosynthesis is a net sink for atmospheric carbon dioxide among these processes.

Common Pitfalls:
Learners sometimes confuse which processes use carbon dioxide and which release it. A useful memory aid is that photosynthesis starts with carbon dioxide, while combustion and respiration end with carbon dioxide. Thinking of photosynthesis as carbon capture and storage in plant biomass can also help keep the direction of the flow clear.

Final Answer:
The correct answer is photosynthesis in green plants, algae, and some bacteria because photosynthesis removes carbon dioxide from the atmosphere and converts it into organic molecules, unlike combustion and respiration which release carbon dioxide.