The U.S
but he did not discover it because there was people who lived there
Explanation:
A comma should follow a dependent clause when the dependent clause comes first in a sentence. A dependent clause is the clause which cannot stand alone in its meaning on the other hand independent clause refers to the phrase which can stand alone, though both have a subject and a verb.
the answer is the third option
Exemplar basically means a typical example, or model, of a concept or role. However the meaning can be extended to mean he best example of a concept or role. For instance, someone might say that you are an exemplar student, which can mean that you are a great example, or model, of a student.