The Telephone
Alexander Graham Bell won a United States patent for the telephone in 1876. A patent meant that no one else could claim that they had invented the telephone. Bell began working with telegraph machines. He wanted to send sound waves over a telegraph wire using a multi-reed system. It could be tuned like a harp. He did not have the equipment to experiment with his idea.
Then Alexander met Thomas Watson. Watson was an electrical designer who became Alexander’s assistant. They found that only one reed was needed to make sounds. Together the men built a telegraph that could send sounds. The waves did not sound like voices yet. On March 7, 1876, Bell received the patent for his invention.
Bell kept working on the telephone. On March 10 of the same year, Bell and Watson made the telephone work. Bell and Watson then improved the telephone. In August 1876, Bell sent a telegram to a town five miles away. People in the telegraph office could hear voices on the telephone. The next day, Bell strung a telephone wire across six miles. The message sent over the telephone wire could be heard clearly. This showed that the telephone worked over long distances.
Bell’s invention became popular very quickly. By 1886, 150,000 people in the United States owned a telephone. Alexander Bell continued to invent for the rest of his life. The telephone remains the most important of his inventions.

Which detail from the third paragraph is most important to include in a summary of the passage?

A. Bell sent a telegram to a town five miles away.

B. Bell and Watson made the telephone work.

C. Bell's telephone used wires to transmit voices.

D. Bell sent his telegram from a telegraph office.