Answer:
Astronomers often develop their ideas D) in a team
Step-by-step explanation:
A collective noun is a noun that is normally in its singular form but that refers to more than one person, animal, thing or concept considered as a single entity. The word “team,” is an example of collective noun because it is singular but it refers to a group or two or more people or animals. Other examples are congregation, class, herd, flock, gang, mob, group, and family.
Option D, then, is the correct answer because it completes the sentence with a collective noun.