Which of the following plant hormones delays leaf senescence (aging)? MCQ with Answer and Explanation

Question
Which of the following plant hormones delays leaf senescence (aging)?
A. Ethylene
B. Abscisic acid
C. Auxin
D. Cytokinin
Answer: Option D
Solution (By JKSSB Mock Tests)
Cytokinins are plant hormones that promote cell division, delay senescence by preventing chlorophyll degradation, and stimulate nutrient mobilization. Ethylene promotes ripening and senescence, abscisic acid promotes abscission and dormancy, auxin is involved in cell elongation. Cytokinins are synthesized in roots and transported upward. They are used to prolong the shelf life of leafy vegetables.
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Question #1
Mendel's law of segregation is based on the separation of:
A. Sister chromatids
B. Homologous chromosomes during meiosis I
C. Non-homologous chromosomes
D. Centromeres
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Correct Answer: Option B

Explanation:
The law of segregation states that two alleles of a gene segregate during gamete formation, which corresponds to the separation of homologous chromosomes in anaphase I.
This question belongs to: Science Biology
Question #2
Which radioactive isotope is commonly used for dating relatively recent fossils (up to about 50,000 years old)?
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Correct Answer: Option D

Explanation:
Carbon-14 (radiocarbon) dating is used to determine the age of organic materials up to about 50,000 to 60,000 years old. Living organisms absorb Carbon-14 from the atmosphere. When they die, absorption stops, and the Carbon-14 decays at a known rate (half-life of 5,730 years). By measuring the remaining Carbon-14, the age of the fossil can be calculated.
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The specific gravity of normal urine is approximately:
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D. 1.050-1.100
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Correct Answer: Option B

Explanation:
Urine specific gravity, a measure of solute concentration, normally ranges from 1.015 to 1.030. It varies with hydration status: low when dilute (after drinking), high when concentrated (dehydration). Diabetes insipidus shows low SG, diabetes mellitus may show high due to glucose.
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