Archaeologists have estimated that the pre-Columbian Native American city of Cahokia, located across the Mississippi River
from modern-day St. Louis, Missouri, had as many as 20,000 inhabitants in the year 1150 ______ it one of the largest cities in
North America at the time.
CE making
CE. Making
CE, making
CE; making
Choice C is the best answer. The phrase “making…at the time” provides additional information about Cahokia that’s not
required for the sentence to make sense or function grammatically. As a nonessential supplement, this phrase should be
separated from the rest of the sentence with a comma.
Choice A is incorrect. This choice results in a run-on sentence. The nonessential descriptive aside “making…at the time”
needs to be separated from the rest of the sentence with a comma. Choice B is incorrect. This choice results in a sentence
fragment. “Making…at the time” doesn’t have a subject and can’t stand on its own as a sentence. Thus, it can’t be separated
from the rest of the sentence with a period. Choice D is incorrect. This choice results in a punctuation error. “Making…at the
time” doesn’t have a subject and can’t stand on its own as an independent clause. Since a semicolon can only link two
independent clauses, using one here creates an error.