Complete the sentences with the correct form of the verbs

1. Radiation
   [ ]
   by Pierre and Marie Curie in 1900.
2. Experiments in the medical university
   [ ]
   every day.
3. An important discovery
   [ ]
   by Newton when he was resting under an apple tree.
4. The gravity theory
   [ ]
   many times so far.
5. The telephone
   [ ]
   in the 1870s.
6. New methods
   [ ]
   nowadays by teachers and lecturers to organise the studying process better.
7. A lot of research must
   [ ]
   to study side effects of new drugs.
8. Many tests and trials
   [ ]
   to prove safety of a new method.
9. People can
   [ ]
   to act as guinea pigs for medical experiment.