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Science — CBSE Class 10 board question

Q1. [1]
Assertion (A) : Blood clotting prevents excessive loss of blood. Reason (R) : Blood clotting is due to blood plasma and white blood cells present in the blood.
  1. (a) Both (A) and (R) are true and (R) is the correct explanation of (A).
  2. (b) Both (A) and (R) are true, but (R) is not the correct explanation of (A).
  3. (c) (A) is true, but (R) is false.
  4. (d) (A) is false, but (R) is true.
Previously asked in CBSE board exam
2023 31/1/1 Q19
Generated by claude-sonnet-4-6 · 2026-06-11 09:47 · grounding rag
Model Answer

(c) (A) is true, but (R) is false.

Assertion is correct — blood clotting does prevent excessive blood loss. However, clotting is caused by platelets (thrombocytes), not by plasma and white blood cells (WBCs).

Source: Life Processes, Section 5.4.1 (Maintenance by platelets)

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Explanation

The textbook clearly states: "the blood has platelet cells which circulate around the body and plug these leaks by helping to clot the blood at these points of injury." WBCs fight infection; they do not cause clotting. Plasma transports substances but is not the agent of clotting. Since the Reason incorrectly names WBCs and plasma instead of platelets, R is false, making option (c) correct.

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