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In an experiment, a leaf was kept in light with its stalk in water, but inside a closed jar with a dish of KOH. Another identical leaf was kept in a similar jar without KOH. After testing with iodine, the difference observed is best explained by the

(a) absence of CO₂ in the first jar Correct
(b) presence of excess O₂ in the second jar Your answer
(c) absence of light in the first jar Your answer
(d) absence of water in the first jar Your answer

Your answer: Correct answer: (a)

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Explanation

Why (a) is correct

KOH absorbs CO₂. The leaf in the KOH jar had no CO₂, so it made no starch, while the other leaf did.

Why the other options are wrong

(b) · your answer Excess O₂ was not the variable.
(c) · your answer Both jars were in light.
(d) · your answer Both leaves had water through their stalks.

NCERT point: This experiment shows that CO₂ is needed for photosynthesis.

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