According to the textbook, Alexander Graham Bell's interest in the telephone was derived from his background in vocal physiology and his work teaching the deaf to speak. His breakthrough experiment took place on June 2, 1875, when he and his assistant Thomas Watson were working on a harmonic telegraph. A reed stuck on Watson's transmitter converted an intermittent current into a continuous current, which Bell heard on his receiver — confirming that sound could be transmitted electrically. Bell was awarded the patent on March 7, 1876. His original design was indeed a modified telegraph that could transmit true sound. Option C is the incorrect statement: Bell did not simply add a speaker to Morse's telegraph; he conducted years of experimental work on sound and electricity before arriving at a working telephone. His breakthrough was a genuine scientific achievement rooted in his study of human speech and vocal physiology.