Assertion (A): Red blood cells lack a nucleus in mammals. Reason (R): The absence of a nucleus allows more space for hemoglobin, increasing oxygen-carrying capacity. MCQ with Answer and Explanation

Assertion (A): Red blood cells lack a nucleus in mammals.
Reason (R): The absence of a nucleus allows more space for hemoglobin, increasing oxygen-carrying capacity.
A. A is true, but R is false.
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 of A.
D. A is false, but R is true.
Answer: Option C
Solution (By JKExamLibrary)
Mature mammalian RBCs are anucleate, having lost their nucleus during maturation. This provides more space for hemoglobin, enhancing oxygen transport. The reason correctly explains the assertion. Nucleated RBCs are found in other vertebrates.

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The scientist who coined the term 'cell' was:
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B. Robert Hooke
C. Antonie van Leeuwenhoek
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Correct Answer: Option B


Explanation:
Robert Hooke, in 1665, observed thin slices of cork under a compound microscope and saw box-like structures he named 'cells'. Leeuwenhoek observed live cells, Brown discovered the nucleus, Virchow proposed cells arise from cells.

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Consider the following statements about the circulatory system:
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Correct Answer: Option D


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