Which phrase best describes the classification of these two organisms dog and cat?

The best phrase to describe the classification of dogs and cats is mammals.

Here's why:

* Domain: Eukarya (both have complex cells with a nucleus)

* Kingdom: Animalia (both are multicellular and heterotrophic)

* Phylum: Chordata (both have a backbone)

* Class: Mammalia (both have fur, give birth to live young, and nurse their offspring)

While dogs and cats are in the same class, they belong to different orders, families, and genera.