What was Bell trying to do before he invented the telephone?

Câu hỏi: Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer for each of the questions from 35 to 42.
In the 1870s, two inventors-Elisha Gray and Alexander GrahamBell - independently developed devices for transmitting speech electrically, an invention which would become known as the telephone. Both men rushed their respective designs to the patent office within hours of each other; however, Bell patented his phone first. The telegraph and telephone are both wire-based electric systems, and Bell's success with the telephone was a direct result of his attempts to improve the telegraph.
When Bell began experimenting with electrical impulses, the telegraph had been an established means of communication for more than 30 years. It was a highly successful system, but ữsdot-and-dash Morse code was limited in terms of sending and receiving. Bell's extensive understanding of sound and knowledge of music contributed to his concept of transmitting multiple messages over one wire simultaneously. His "harmonic telegraph" was based on the principle that several note could be sent simultaneously along the same wire if the notes or signals differed in pitch.
What was Bell trying to do before he invented the telephone?
A. He was trying to beat Elisha Gray to the patent office.
B. He was trying to impress his father-in-law.
C. He was trying to improve the telegraph.
D. He was trying to transmit speech electronically.