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A
Respiration
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B
Photosynthesis
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C
Digestion
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D
Fermentation
Why this is the answer
Photosynthesis is the process by which plants (and some other organisms) use sunlight to convert carbon dioxide and water into glucose (sugar) and oxygen. It occurs mainly in the chloroplasts, which contain the green pigment chlorophyll that captures light energy. Respiration is almost the reverse process — using oxygen to release energy from glucose. Photosynthesis is fundamental to life because it produces oxygen and forms the base of most food chains. The basic equation is: carbon dioxide + water + light energy → glucose + oxygen.
Source: ASVAB GS, Photosynthesis