The correct answer is B.“Researchers' estimates of the actual number vary from three hundred to six thousand, but everyone knows that ads are everywhere.” (paragraph 1)
Step-by-step explanation:
The function of coordinating conjunctions is to join or connect two elements of the same importance, especially two independent clauses. This means the section the conjunction connects are complete sentences with complete meaning. Additionally, this category of conjunctions includes words such as but, so, and, or, etc.
In this context, the sentence “Researchers' estimates of the actual number vary from three hundred to six thousand, but everyone knows that ads are everywhere.” is the one with a coordinating conjunction because in this, the conjunction "but" that shows contrast is used to link to complete sentences "Researchers' estimates of the actual number vary from three hundred to six thousand" and "everyone knows that ads are everywhere".