Read the given statements and conclusions carefully. Assuming that the information given in the statements is true, even if it appears to be at variance with commonly known facts, decide which of the given conclusions logically follow(s) from the statements. Statements: All Plane are Plain. All Helicopter are Plain. Some Helicopter are Passenger. Conclusions:
I. Some Plane are Passenger.
II. Some Plain are Passenger.
III. No Plain is helicopter.
IV. No Plane are Passenger.

All Plane are Plain (A) +  All Helicopter are Plain (A) → Conversion → Some Plain are Helicopter (I) → No conclusion. Hence neither conclusion I nor IV follows bit it will make a complementary pair. Hence either conclusion I or IV follows. Some Helicopter are Passenger → Conversion → Some Passenger are Helicopter (I) + All Helicopter are Plain (A) → Some Passenger are Plain (I) → Conversion → Some Plain are Passenger (I). Hence conclusion II follows. All Helicopter are Plain (A) → Conversion → Some Plain are Helicopter (I). Hence conclusion III does not follow.