Three statements are given followed by three conclusions numbered I, II and III. Assuming the statements to be true, even if they seem to be at variance with commonly known facts, decide which of the conclusions logically follow(s) from the statements. Statements: All crows are parrots. All eagles are parrots. All parrots are birds. Conclusions: I. No crow is a bird. II. Some birds are eagles. III. All birds are crows.

Correct — D. Chain the statements: crows sit inside parrots, eagles sit inside parrots, parrots sit inside birds.

I. No crow is a bird — every crow is a parrot and every parrot is a bird, so every crow is a bird. I is contradicted, not merely unsupported.

II. Some birds are eagles — eagles inside parrots inside birds makes all eagles birds, and a universal of that shape yields the particular. II follows.

III. All birds are crows — birds is the widest class and nothing shrinks it to crows.

II alone survives, so option (d).

Why the others are wrong

• (a)
  All conclusions follow. — All conclusions follow needs conclusion I to hold, but the chain crow to parrot to bird makes every crow a bird — the exact opposite of I.
• (b)
  Both conclusions I and III follow. — I and III fails twice over: I is contradicted by the chain, and III would require birds, the widest class, to be no larger than crows.
• (c)
  Either conclusion II or III follows. — Either II or III is the wording for a complementary pair, where one must be true and one false. II already follows outright, so no either-or is needed.

Three-statement syllogisms are settled by containment, not by what the words mean in the world. Draw the chain.

Crows and eagles both sit inside parrots, and parrots sits inside birds — so crows and eagles both sit inside birds.

Two rules do most of the work. A universal affirmative, all A are B, always yields the particular some B are A, because A is treated as non-empty.

And containment never runs upward: all parrots are birds tells you nothing about the birds that are not parrots.

Key facts

• All A are B licenses some B are A, because the classes in this format are taken as non-empty.
• Containment runs one way, so all parrots are birds does not make all birds parrots.
• An either-or answer is correct only when neither conclusion holds alone but one of the two must be true.

Common traps

• Rejecting some birds are eagles because the statement said eagles are parrots, not birds.
• Using the real-world fact that crows are birds as evidence instead of the chain.
• Reaching for an either-or option when one conclusion already follows outright.

No directly related past PYQ was found.