CUET · BIOLOGY · PYQ PAPER 2025

What is the primary function of the aeration tanks in the secondary treatment of sewage?

A To remove solid waste through filtration
B To allow the growth of aerobic microbes that consume organic matter
C To reduce the BOD of the effluent using chemicals
D To settle the activated sludge

Verified Solution

Answer & Solution

Correct Answer

(B) To allow the growth of aerobic microbes that consume organic matter

Step-by-step Solution

Detailed explanation

To allow the growth of aerobic microbes that consume organic matter.

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

Same subject

Match List I with List II

List - I	List - II
(A) Both the species are benefitted	(I) Competition
(B) One of the species is benefitted but the other is harmed	(II) Parasitism
(C) One of the species is benefitted but the other is neither benefitted nor harmed	(III) Commensalism
(D) Both the species are harmed	(IV) Amensalism
	(V) Mutualism

Choose the correct answer from the options given below:

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