The correct answers are:
1. Tursiops;
Tursiops is a more specific taxon than mammalia as it is referring to only a single branch from the very large mammalian taxon.
2. Cetacea;
Cetacea is a more specific taxon than Chordata because it is referring to only a relatively small group of animals that are closely related, while Chordata is a taxon that includes all vertebrates.
3. Truncatus;
Truncatus is more specific taxon than Delphinidae because it is referring to a species, while Delphinidae is referring to the whole family in which the Truncatus species belongs.
4. Truncatus;
Truncatus is more specific taxon than Tursiops as it is referring to a species, while Tursiops is referring to a whole branch of closely related species.