Free Human Body and Health MCQs with Answers

551. The vitamin which is generally excreted by humans in urine is__________?

• A. Vitamin A
• B. Vitamin B
• C. Vitamin B12
• D. Vitamin C

Explanation: Vitamin C is water-soluble, so the body stores little of it and excess amounts are removed in urine. Vitamins A and B12 are stored more substantially, while vitamin B is an imprecise group name.

552. The Virus of AIDS affects the growth of_____________?

• A. Hemoglobin
• B. RBCs in blood
• C. T cells in blood
• D. Grey Cells in blood

Explanation: HIV, the virus that causes AIDS, attacks CD4 helper T cells and progressively weakens immune function. It does not specifically target haemoglobin or red blood cells.

553. Muscle fatigue is caused by the accumulation of___________?

• A. Uric acid
• B. Lactic acid
• C. Oxalacetic acid
• D. Fyruvie acid

Explanation: During intense exercise with insufficient oxygen, muscles produce lactic acid through anaerobic respiration, and its associated metabolic changes contribute to fatigue. Uric acid is mainly a waste product of purine breakdown.

554. Which of the following vitamins is synthesized in the body by intestinal bacteria_______?

• A. Vitamins B1
• B. Vitamins B12
• C. Vitamins E
• D. Vitamins K

Explanation: Intestinal bacteria can synthesize vitamin K, and this is why vitamin K is the standard answer in basic biology questions. The amount produced may not fully meet a person’s needs, so dietary intake remains important.

555. Cow milk is a rich source of____________?

• A. vitamin C
• B. vitamin B
• C. vitamin A
• D. vitamin K

Explanation: Cow’s milk is a recognised source of vitamin A, particularly in its fat component and in fortified milk. It also contains some B vitamins, but vitamin C and vitamin K are not its main strengths.

556. AIDS virus is______________________

• A. Single-stranded RNA
• B. Single-stranded DNA
• C. Double-stranded RNA
• D. Double-stranded DNA

Explanation: HIV, the virus that causes AIDS, carries its genetic material as single-stranded RNA. It uses reverse transcriptase to make DNA inside the host cell, but the virus itself is classified as an RNA virus.

557. Quantity of fresh air required for a man is 1000 cubic feet of air for every____________?

• A. 5 minutes
• B. 10 minutes
• C. 15 minutes
• D. 20 minutes

Explanation: The traditional ventilation standard used in such questions is about 1,000 cubic feet of fresh air per person every 20 minutes. This replaces exhaled air and helps limit the buildup of carbon dioxide indoors.

558. Approximately, how many times each day do our heart valves open and close normally?

• A. 10,000
• B. 1,00,000
• C. 1,50,000
• D. 2,00,000

Explanation: At an average rate of about 70 heartbeats per minute, the valves open and close roughly 100,000 times in 24 hours. The larger figures would require an abnormally high heart rate or count.

559. The 'stone' formed in human kidney consist mostly of_____________?

• A. Calcium oxalate
• B. Sodium acetate
• C. Magnesium sulphate
• D. Calcium

Explanation: Most kidney stones are calcium oxalate, formed when calcium combines with oxalate in concentrated urine. Pure calcium is not the usual composition, although calcium is part of many stones.

560. In eye donation, which one of the following parts of donor's eye is utilized ?

• A. Iris
• B. Lens
• C. Cornea
• D. Retina

Explanation: Eye donation commonly provides the cornea for transplantation because a damaged or opaque cornea can block light from entering the eye. The iris, lens, and retina are generally not the donated transplant tissue in this context.