Ozone layer depletion in the stratosphere is primarily caused by: MCQ with Answer and Explanation

Question
Ozone layer depletion in the stratosphere is primarily caused by:
A. Chlorofluorocarbons (CFCs)
B. Sulfur dioxide
C. Carbon dioxide
D. Methane
Answer: Option A
Solution (By JKExamLibrary)
The ozone layer in the stratosphere protects Earth from harmful ultraviolet (UV) radiation. Its depletion is primarily caused by Chlorofluorocarbons (CFCs), which were widely used in refrigerants, aerosols, and solvents. UV radiation breaks down CFCs, releasing chlorine atoms that catalytically destroy ozone molecules. The Montreal Protocol (1987) was an international treaty to phase out the production of CFCs.
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Question #1
Assertion (A): Humans are ureotelic.
Reason (R): The liver converts ammonia to urea, which is excreted in urine.
A. A true, R false.
B. Both A and R are true, but R is not the correct explanation.
C. A false, R true.
D. Both A and R are true, and R is the correct explanation.
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Correct Answer: Option D

Explanation:
Ammonia, toxic, is converted to less toxic urea in the liver via the urea cycle, then excreted by kidneys. Thus, humans excrete urea (ureotelic). R explains A.
This question belongs to: Science Biology
Question #2
Which of the following is a respiratory disease caused by a coronavirus?
A. Influenza
B. Tuberculosis
C. COVID-19
D. Pneumonia caused by Streptococcus
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Correct Answer: Option C

Explanation:
COVID-19 is caused by SARS-CoV-2, a novel coronavirus. Tuberculosis is bacterial (Mycobacterium). Influenza is caused by influenza viruses (Orthomyxoviridae), not coronavirus. Pneumonia can be bacterial or viral, but the question specifies Streptococcus which is bacterial. COVID-19 emerged in 2019, causing a global pandemic, primarily affecting the respiratory system.
This question belongs to: Science Biology
Question #3
In the male reproductive system, the spermatozoa are stored and mature in the:
A. Prostate gland
B. Epididymis
C. Seminal vesicles
D. Vas deferens
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Correct Answer: Option B

Explanation:
The epididymis is a coiled tube on the posterior surface of the testis where spermatozoa undergo maturation and are stored until ejaculation. Sperm acquire motility here. Seminal vesicles and prostate gland secrete seminal fluid. Vas deferens transports sperm from epididymis to ejaculatory duct. Testes produce sperm and testosterone. Sperm maturation includes gaining ability to fertilize.
This question belongs to: Science Biology
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