The structure that controls the entry of light into the eye by adjusting pupil size is the: MCQ with Answer and Explanation

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The structure that controls the entry of light into the eye by adjusting pupil size is the:

A. Lens

B. Retina

C. Iris

D. Cornea

Answer: Option C

Solution (By JKSSB Mock Tests)

The iris contains smooth muscle fibers (sphincter and dilator) that regulate the diameter of the pupil. The cornea and lens focus light, retina senses it.

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Question #1

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Assertion (A): Plants take in carbon dioxide and release oxygen during the day.
Reason (R): Photosynthesis produces oxygen as a byproduct.

A. A false, R true.

B. Both A and R are true, but R is not the correct explanation.

C. Both A and R are true, and R is the correct explanation.

D. A true, R false.

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Correct Answer: Option C

Explanation:
During daylight, photosynthesis dominates, consuming CO₂ and releasing O₂. The oxygen comes from water splitting. R correctly explains A.

This question belongs to: Science Biology

Question #2

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The element present in the center of the chlorophyll molecule is:

A. Cobalt

B. Magnesium

C. Calcium

D. Iron

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Correct Answer: Option B

Explanation:
Magnesium (Mg²⁺) is the central atom in the porphyrin ring of chlorophyll, crucial for light absorption. Iron is in hemoglobin.

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Question #3

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The scientist who discovered the bacterium Helicobacter pylori and its role in ulcers was:

A. Alexander Fleming

B. Robert Koch

C. Barry Marshall and Robin Warren

D. Louis Pasteur

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Correct Answer: Option C

Explanation:
Marshall and Warren discovered H. pylori in 1982 and proved it causes peptic ulcers, earning the 2005 Nobel Prize. Koch discovered TB, Pasteur vaccines, Fleming penicillin.

This question belongs to: Science Biology

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