The year was 1849, and Antonio Meucci, a man trained in engineering, was experimenting with electricity. He and a doctor were trying to determine if electric shock could be used to cure illnesses. One day, when he turned on the switches to treat a patient in another room, he heard the patient yelp. However, the voice had not come from the next room—it had come from the copper wire that ran between them! Following that fateful day, Meucci left his medical experiments behind. Instead, he set a goal to develop that talking wire into a machine he called a “talking telegraph.” After six years of trials and tests, he was able to build a working model. Meucci found it to be a useful device almost immediately.

Based on the sequence of events in the excerpt, which sentence best states a cause-and-effect relationship?

Because Antonio Meucci was a trained engineer, he was able to invent a “talking telegraph.”
Because electricity was used to cure sickness, Antonio Meucci invented the “talking telegraph.”
Because the device was so useful, Antonio Meucci invented the “talking telegraph.”
Because he heard a patient’s yelp through a copper wire, Antonio Meucci invented the “talking telegraph.