Final answer:
The sentence that best addresses Carla's comparison-and-contrast essay purpose, regarding different care needs of cats and dogs, is statement D, which highlights the exercise requirements of dogs compared to cats.
Step-by-step explanation:
The sentence that specifically addresses the purpose of the paragraph, which is to show how the care of cats and dogs is different, is option D: Dogs must be walked or exercised daily, while cats do not need to be walked. This sentence contrasts the daily physical needs of dogs with those of cats, highlighting a clear difference in their care requirements. In a comparison-and-contrast essay, the focus is on delineating the differences and similarities between two subjects, and this sentence directly compares two aspects of pet care specific to each type of pet.