【分析解答题】

Since 1875, whenAlexander GrahamBell first discovered how to send the human voice along wires, the telephone has been one of the world’s most utilized and essential methods of communication. The first telephone exchange inAmerica was established in 1878 and served a total of 21 people.At that time, operators would answer a call and connect two parties by completing an electrical circuit. Little could those operators envision that, one century later, calls would be transmitted along optical fibers and, soon after, would become totally wireless and portable. The idea of orbiting satellites picking up millions of calls and relaying them across the planet would have been unimaginable.

Select the sentence that establishes the scope of the earliest telephone communications.