What contribution did Alexander Graham Bell make to industrial growth in the U. S.?

D. He patented the telephone.

Telegraphy

Explanation:

Alexander Graham Bell, born March 3, 1847, Edinburgh, Scotland-died August 2, 1922, Beinn Bhreagh, Cape Breton Island, Nova Scotia, Canada, Scottish-born American inventor, scientist, and teacher of the deaf whose foremost accomplishments were the invention of the telephone in 1876 and the refinement of the phonograph (1886). Alexander was born to Alexander Melville Bell and Eliza Grace Symonds. His mother was almost deaf, and his father taught elocution to the deaf, influencing Alexander's later career choice as teacher of the deaf. At age 11 he entered the Royal High School at Edinburgh, but he did not enjoy the compulsory curriculum, and he left school at age 15 without graduating. In 1865 the family moved to London. Alexander passed the entrance examinations for University College London in June 1868 and matriculated there in the autumn. However, he did not complete his studies, because in 1870 the Bell family moved again, this time immigrating to Canada after the deaths of Bell's younger brother Edward in 1867 and older brother Melville in 1870, both of tuberculosis. The family settled in Brantford, Ontario, but in April 1871 Alexander moved to Boston, where he taught at the Boston School for Deaf Mutes. He also taught at the Clarke School for the Deaf in Northampton, Massachusetts, and at the American School for the Deaf in Hartford, Connecticut. One of Bell's students was Mabel Hubbard, daughter of Gardiner Greene Hubbard, a founder of the Clarke School. Mabel had become deaf at age five as a result of a near-fatal bout of scarlet fever. Bell began working with her in 1873, when she was 15 years old. Despite a 10-year age difference, they fell in love and were married on July 11, 1877. They had four children, Elsie (1878-1964), Marian (1880-1962), and two sons who died in infancy. While pursuing his teaching profession, Bell also began researching methods to transmit several telegraph messages simultaneously over a single wire-a major focus of telegraph innovation at the time and one that ultimately led to Bell's invention of the telephone. In 1868 Joseph Stearns had invented the duplex, a system that transmitted two messages simultaneously over a single wire. Western Union Telegraph Company, the dominant firm in the industry, acquired the rights to Stearns's duplex and hired the noted inventor Thomas Edison to devise as many multiple-transmission methods as possible in order to block competitors from using them. Edison's work culminated in the quadruplex, a system for sending four simultaneous telegraph messages over a single wire. Inventors then sought methods that could send more than four; some, including Bell and his great rival Elisha Gray, developed designs capable of subdividing a telegraph line into 10 or more channels. These so-called harmonic telegraphs used reeds or tuning forks that responded to specific acoustic frequencies. They worked well in the laboratory but proved unreliable in service. A group of investors led by Gardiner Hubbard wanted to establish a federally chartered telegraph company to compete with Western Union by contracting with the Post Office to send low-cost telegrams. Hubbard saw great promise in the harmonic telegraph and backed Bell's experiments. Bell, however, was more interested in transmitting the human voice. Finally, he and Hubbard worked out an agreement that Bell would devote most of his time to the harmonic telegraph but would continue developing his telephone concept.