AI-generated practice question — model-generated for extra practice, not a previous-year CBSE board question.
Answer: C — Pyruvate
In all forms of respiration, the first step is glycolysis, which occurs in the cytoplasm and breaks down glucose (6-carbon) into pyruvate (3-carbon molecule).
The question tests knowledge of the first common step of respiration. Lactic acid and ethanol are end products of anaerobic respiration (in different organisms), not the first product. ATP is the energy currency, not an intermediate. Pyruvate is always the correct answer as it is the universal first product of glucose breakdown (glycolysis), common to both aerobic and anaerobic pathways. This links to Exercise Q4 in the chapter, which also tests knowledge of where pyruvate is further broken down (mitochondria).