Which one of these is NOT a valid syllogism: All mammals are warm-blooded. All warm-blooded creatures are animals. Therefore, all mammals are animals?

The reasoning behind the provided answer being correct is based on the structure and principles of syllogisms. A syllogism is considered valid when the conclusion logically follows from its premises. In this case, the premises are:

1. All mammals are warm-blooded.

2. All warm-blooded creatures are animals.

From these premises, the conclusion "Therefore, all mammals are animals" is logically sound because it connects the characteristics of being a mammal and being warm-blooded, ultimately linking them both to the broader category of animals.

The logical flow follows a traditional format in syllogistic reasoning, where the inclusion of one category within another allows for valid conclusions about their relationships. In this scenario, since all mammals fall under the subset of warm-blooded creatures, and all warm-blooded creatures are animals, it consequently confirms that all mammals must also be animals. Thus, the argument is valid based on its structure.

The other choices present different perspectives that do not reflect the logical validity of the syllogism in question. Hence, it’s important to recognize the accurate relationship among the categories involved to affirm that the statement is indeed a valid syllogism.