The Biological Oxygen Demand (BOD) measures: MCQ with Answer and Explanation

The Biological Oxygen Demand (BOD) measures:
A. The oxygen produced by plants
B. The oxygen in blood
C. The oxygen content in the atmosphere
D. The amount of oxygen required by microorganisms to decompose organic matter in water
Answer: Option D
Solution (By JKExamLibrary)
BOD is a measure of organic pollution in water bodies. High BOD indicates high levels of biodegradable organic matter, leading to oxygen depletion as microorganisms break it down. This can cause fish kills and eutrophication. Clean water has low BOD (

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Practice More Biology Questions

Question #1
Consider the following statements about the nitrogen cycle:
1. Nitrogen fixation converts N₂ to ammonia.
2. Nitrification converts ammonia to nitrates.
3. Denitrification returns nitrogen to the atmosphere.
Which of the above is/are correct?
A. 2 and 3 only
B. 1 and 3 only
C. 1, 2, and 3
D. 1 and 2 only

Correct Answer: Option C


Explanation:
All three processes are part of the nitrogen cycle: fixation (N₂ → NH₃), nitrification (NH₃ → NO₂⁻ → NO₃⁻), and denitrification (NO₃⁻ → N₂).

This question belongs to: Science Biology
Question #2
Identify the correct statement about vitamins and minerals:
A. Vitamin C is a fat-soluble vitamin.
B. Calcium is essential for bone formation.
C. Iron is required for blood clotting.
D. Iodine deficiency causes anemia.

Correct Answer: Option B


Explanation:
Calcium is a major component of bones. Vitamin C is water-soluble, iron is for hemoglobin (oxygen transport), iodine deficiency causes goiter, anemia is from iron/B₁₂/folate deficiency.

This question belongs to: Science Biology
Question #3
Which of the following statements about genes and alleles is correct?
A. Dominant alleles mask the effect of recessive alleles.
B. An individual with two identical alleles is heterozygous.
C. A gene is a variant form of an allele.
D. Recessive alleles are always expressed in the phenotype.

Correct Answer: Option A


Explanation:
Dominant alleles express their trait when present, masking recessive alleles. A gene is a DNA segment; alleles are its variants. Homozygous means identical alleles, recessive expressed only in homozygous state.

This question belongs to: Science Biology