UPSC Prelims 2002 · General Studies

Question 26: Science and Technology

With reference to the blood in a normal person, which one of the following statements is correct?

aCompared to arteries, veins are less numerous and hold less of the body’s blood at any given time

bBlood cells constitute about 70 % of the total volume of the blood

cWhite Blood Cells (WBC) are made by lymph nodes only

dThe blood has more platelets than WBC

AnswerThe answer is (d).

Platelets number about 1.5 to 4 lakh per microlitre of blood, while white blood cells number only about 4,000 to 11,000, so the blood has far more platelets than WBC. The other statements fail: veins hold most of the body's blood at rest (roughly two-thirds), blood cells make up only about 45 percent of blood volume with plasma the other 55 percent, and WBCs are also made in the bone marrow, not by lymph nodes alone.

Why each option is right or wrong

(a) Veins hold more blood than arteries, about two-thirds of the total, so this is reversed.
(b) Cells are about 45 percent of blood volume; plasma is the larger part.
(c) WBCs are also produced in the bone marrow, not by lymph nodes only.
(d) Right: platelets (lakhs per microlitre) outnumber WBC (thousands).

Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2002, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.