Given below are two statements regarding circulation of blood in fishes.
Statement I: Heart of fish contains only deoxygenated blood.
Statement II: Fishes show single circulation and blood passes through heart only once during each cycle.
In light of above statements, choose the correct answer from the options given below.

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.