The structure that carries oxygenated blood from the lungs to the heart is the: MCQ with Answer and Explanation

The structure that carries oxygenated blood from the lungs to the heart is the:
A. Pulmonary vein
B. Superior vena cava
C. Pulmonary artery
D. Aorta
Answer: Option A
Solution (By JKSSB Mock Tests)
The four pulmonary veins drain oxygen-rich blood from the lungs into the left atrium. The pulmonary artery carries deoxygenated blood from right ventricle to lungs. Vena cava brings deoxygenated blood to right atrium.

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Practice More Biology Questions

Question #1
The human ovum completes meiosis II at which stage?
A. During embryonic development
B. Before ovulation
C. After fertilization, upon sperm entry
D. At fertilization

Correct Answer: Option C


Explanation:
The secondary oocyte is arrested in metaphase II of meiosis and is ovulated. Meiosis II is completed only when a sperm penetrates the oocyte, producing a mature ovum and a second polar body. If fertilization does not occur, the secondary oocyte degenerates. This ensures that the egg is only fully mature upon fertilization.

This question belongs to: Science Biology
Question #2
The phase of the cardiac cycle when the ventricles relax and fill with blood is called:
A. Atrial contraction
B. Diastole
C. Ejection phase
D. Systole

Correct Answer: Option B


Explanation:
Diastole is the relaxation phase of the cardiac cycle, during which the ventricles fill with blood from the atria. Systole is the contraction phase, pumping blood out. Atrial contraction (atrial systole) contributes to ventricular filling. Ejection phase is part of ventricular systole when blood is ejected. Normal diastolic and systolic pressures are 80 and 120 mmHg respectively.

This question belongs to: Science Biology
Question #3
Assertion (A): Plants wilt in salty soil.
Reason (R): High salinity causes water to move out of root cells by osmosis.
A. Both A and R are true, but R is not the correct explanation.
B. A false, R true.
C. A true, R false.
D. Both A and R are true, and R is the correct explanation.

Correct Answer: Option D


Explanation:
Saline soil has lower water potential, causing exosmosis from root cells, leading to plasmolysis and wilting. R correctly explains A.

This question belongs to: Science Biology