Open the brackets and put the verbs into the correct tense. Write full forms.

Alexander Graham Bell probably did not know at the time that he invented one of the most popular devices in modern history. In fact, he worked on a hearing device when he stumbled on the invention of the telephone. Bell tried desperately to find some way to help deaf people hear and communicate with others because he experienced deaf people's problems first-hand. Bell went on to invent numerous other things, but we will always remember him for bringing us the telephone.