Помогите, пожалуйста! Passive voice.
1. Hundreds of people ..... by the factory this year.
a. employed
b. were employed
c. have been employed

2. Four people ..... to the conference yesterday.
a. were invited
b. invited
c. are invited

3. Many accidents ..... by dangerous chemicals.
a. caused
b. are caused
c. will have been caused

4. Our plan ..... by the members of the committee now.
a. was discussed
b. is being discussed
c. is discussed

5. The building site ..... mostly ..... with water.
a. is ... covered
b. will ... be covered
c. had ... been covered
6. The university of Michigan is one of the best universities in the United States and it ..... in Ann Arbor.
a. located
b. are located
c. is loсated
7. This software ........ by our IT specialist last month.
a. was developed
b. had been developed
c. is developed

8. The letters ................. at the moment.
a. will be typed
b. are being typed
c. are typing

9. The first 3D printer ................. by Chuck Hull in 1983.
a. was invented
b. has been invented
c. invented
10. Most people think that this device …… after its inventor.
a. be called
b. is called
c. was being called

11. We checked that all the dооrs ……. before we left the office.
a. were closed
b. are closed
c. had been closed

12. What a wonderful lecture! I’m sure it ….. even in a few years’ time.
a. will not be forgotten
b. will not forgotten
c. will be not forgotten