Complete the sentences with the correct form of the verbs from the list.

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, , , , , , , ,
Radiation
was discovered
by Pierre and Marie Curie in 1900.
Experiments in the medical university

every day.
An important discovery

by Newton when he was resting under an apple tree.
The gravity theory

many times so far.
The telephone

in the 1870s.
New methods

nowadays by teachers and lecturers to organise the studying process better.
A lot of research must

to study side effects of new drugs.
Many tests and trials

to prove safety of a new method.
People can

to act as guinea pigs for medical experiment.

1. Radiation was discovered by Pierre and Marie Curie in 1900.
2. Experiments in the medical university are conducted every day.
- Explanation: This sentence talks about the frequency of experiments happening in a medical university. The verb "conduct" means to carry out or perform, and in this case, it refers to the act of doing experiments. The present simple tense is used because it expresses a habitual action.
3. An important discovery was made by Newton when he was resting under an apple tree.
- Explanation: This sentence describes a specific event in the past when Newton made an important discovery. The passive voice is used here because the focus is on the discovery, not on who performed it. The past simple tense is used to indicate a single event in the past.
4. The gravity theory has been tested many times so far.
- Explanation: This sentence talks about the repeated action of testing the gravity theory. The present perfect tense is used to indicate that the action started in the past and has continued up to the present moment. The verb "test" is in the passive voice because it is the theory that has been tested.
5. The telephone was invented in the 1870s.
- Explanation: This sentence talks about the time of the invention of the telephone. The passive voice is used here because the focus is on the invention itself, not on who performed it. The past simple tense is used to indicate a single event in the past.
6. New methods are used nowadays by teachers and lecturers to organize the studying process better.
- Explanation: This sentence talks about the current practice of using new methods by teachers and lecturers. The present simple tense is used because it expresses a habitual action. The verb "use" is in the passive voice because it indicates that the methods are being applied by teachers and lecturers.
7. A lot of research must be conducted to study side effects of new drugs.
- Explanation: This sentence talks about the necessity of conducting research to study side effects. The modal verb "must" is used to express obligation or necessity. The passive voice is used here because the focus is on the action of conducting research, not on who performs it.
8. Many tests and trials have to be done to prove the safety of a new method.
- Explanation: This sentence talks about the necessity of doing tests and trials to prove safety. The modal verb "have to" is used to express obligation or necessity. The passive voice is used here because the focus is on the action of doing tests and trials, not on who performs them.
9. People can volunteer to act as guinea pigs for medical experiments.
- Explanation: This sentence talks about the possibility of volunteering to act as guinea pigs. The modal verb "can" is used to express ability or permission. The active voice is used here because the focus is on people who perform the action of volunteering.