The site of gas exchange in the human lungs is: MCQ with Answer and Explanation

The site of gas exchange in the human lungs is:
A. Alveoli
B. Bronchi
C. Bronchioles
D. Trachea
Answer: Option A
Solution (By JKSSB Mock Tests)
Alveoli are tiny thin-walled air sacs surrounded by pulmonary capillaries. Oxygen diffuses into blood, and carbon dioxide diffuses out.

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Practice More Biology Questions

Question #1
The normal Glomerular Filtration Rate (GFR) in a healthy adult is approximately:
A. 125 ml/min
B. 75 ml/min
C. 500 ml/min
D. 250 ml/min

Correct Answer: Option A


Explanation:
The Glomerular Filtration Rate (GFR) is the volume of fluid filtered from the renal glomerular capillaries into the Bowman's capsule per unit time. In a healthy adult, the normal GFR is approximately 125 ml per minute, which amounts to about 180 liters per day. Almost all of this filtrate is reabsorbed, leaving only 1.5 liters of urine.

This question belongs to: Science Biology
Question #2
Edward Jenner is credited with developing the first vaccine against:
A. Rabies
B. Tuberculosis
C. Smallpox
D. Polio

Correct Answer: Option C


Explanation:
Edward Jenner, an English physician, is known as the 'father of immunology'. In 1796, he developed the world's first successful vaccine against smallpox. He observed that milkmaids who had contracted cowpox (a mild disease) were immune to smallpox. He inoculated a boy with material from a cowpox blister, successfully conferring immunity to smallpox, thus pioneering the concept of vaccination.

This question belongs to: Science Biology
Question #3
Which vitamin is also known as ascorbic acid?
A. Vitamin B₁
B. Vitamin A
C. Vitamin D
D. Vitamin C

Correct Answer: Option D


Explanation:
Vitamin C, chemically ascorbic acid, is a water-soluble vitamin essential for collagen synthesis, wound healing, iron absorption, and antioxidant function. Its deficiency causes scurvy (bleeding gums, weakness). Vitamin A is retinol, B₁ is thiamine, D is calciferol. Vitamin C is abundant in citrus fruits, guava, amla. It is heat-labile and easily destroyed by cooking.

This question belongs to: Science Biology