The telephone was INVENTED/DISCOVERED by Alexander Graham Bell. Какое слово нужно вставить?

I live in the city of Orsk. It settles down in the Orenburg area. Orsk borrows 80 seat on a population in Russia.
Orsk is considered the second in a commercial significance of the Orenburg area.
Pride of Orsk are Орский the state pedagogical college, as well as branch of the Orenburg state university and branch of the Orenburg state college of management as their pupils borrow prize-winning places in regional and All-Russia Olympiads.
One more pride of Orsk is the hockey command « Southern Urals Mountains » which spends house matches in a palace of sports "Anniversary"
As Orsk — one of large transport units of Russia, through it are carried out numerous passenger and freight traffic.
From the western side of Orsk spurs of the Ural mountains amazing with the beauty tower. In the given district the set of various mountain grasses and trees grows, it is possible to observe wild-growing tulips in the spring. Basically, in local seats weather pleases, as cloudless, in a year here it is more than sunny days.
Crisis in an ecological condition of an environment of Orsk directly depends on industrial pollution. Air in territory of Orsk is considered the most polluted in the Orenburg area.

time that he 1) ........ (invent) one
of the most popular devices in modem history. In fact, he
2)........ (work) on a hearing
device when he 3)........ (stumble)
on the invention of the telephone.
Bell 4) ........ (try) desperately to find
some way to help deaf people hear and
communicate with others because he 5) ........ (live)
with his deaf mother and wife and 6) ........
(experience) deaf people's problems first hand. Bell went on to invent numerous other things, but we
7)........ (always/remember) him for bringing us the
telephone.