Statements: A. All birds are swans.
B. Some skirts are birds.
C. All swans are ducks.
Conclusions: I. Some ducks are birds.
II. Some skirts are ducks.
III. All birds are ducks.
IV. Some birds are not ducks.

Options

A. Only I and II follow
B. Only II and III follow
C. Either III or IV follows
D. I, II and either III or IV follow

Explanation

Conclusion I, III, IV: Subject and predicate are "ducks" and "birds”. relevant statements are A and C. Now, All birds are swans + All ucks = A +A=A=All birds are ducks. Hence, III is valid. Again, e ducks" gives "Some ducks are birds”. Hence, I is valid. III and IV make complementary pair but we do not choose ..either III or IV follows because III has already been accepted.
Conclusion II: Subject=.skirts. and predicate= ducks. Skirts while .ducks. appears in C. But there is no term between B and C. Hence, all three statements are relevant rearrange the three statements. Some sirts are birds + alll are swans + all swans are ducks =I+A+A=(I+A)+A= A=I= Some skirt are ducks. Hence, conclusion II is valid.