1. to be useful, a scientific name has to refer living species.
all living and extinct species.
all species in one habitat.
a single species.

2. several different classes make up .
phylum.
family.
genus.

3. which are the two highest-level taxa in the linnaean and order
domain and phylum
phylum and kingdom
genus and kingdom

4. animals that are warm-blooded, have body hair, and produce milk for their young are grouped in the .
mammalia.
aves.

1. The correct answer would be all living and extinct species.

Scientific name refers to the formal name universally used to denote a particular organism. For example, Homo sapiens is the scientific name of human species.

2. The correct answer would be phylum.

Classification hierarchy can be written as species → genus → family → order → class → phylum → kingdom → Domain.

Thus, the classes make up a phylum.  

3. The most appropriate answer would be phylum and kingdom.

Carolus Linnaeus is also known as the father of taxonomy as he provided the system for classification and naming of the organisms.

He gave 7 levels classification which consisted of species → genus → family → order → class → phylum → kingdom.

4. The correct answer would be mammals.

Mammals are vertebrates which has a unique feature of presence of mammary glands. In females, mammary glands help in milk production which helps in the nourishment of young ones. Other characteristics may include war-blood, the presence of body hairs or furs, et cetera.