To solve this question, the user needs to know the collective nouns for groups of animals. Collective nouns are used to describe groups of specific animals.
In this case, the correct answer is D. A pack of dogs is a group of dogs that hunt or work together. Option A "herd" is used for cattle, sheep, and other grazing animals. Option B "cowardice" is a noun that describes a group of people who are afraid. Option C "school" is used for fish.
Therefore, the answer is: D. Pack.