No bird is a mammal. All mammals are warm-blooded. What necessarily follows?
Correct: B
From 'No B are M' and 'All M are W', we cannot conclude anything definite about birds and warm-bloodedness. The middle term 'mammals' is distributed in the first premise (No B are M) but the conclusion about B and W is not entailed. Birds might or might not be warm-blooded — the premises do not address this. The syllogism does not yield a valid conclusion about birds and warm-blooded animals.