Revising Tenses

3.20. Choose the right variant and complete the following sentences.

1. The students … their laboratory work now.

a) have done b) are doing c) are being done

2. They … on the project for three months.

a) have been working b) has worked c) are working

3. The project … by the end of the month.

a) will finish b) will have been finished c) will be finishing

4. The hypothesis … confirmation at that time.

a) lacks b) lacked c) has lacked

5. Chemical methods of purifying water … much attention to nowadays.

a) are given b) was given c) give

6. The number of components that can be squezeed on the chip … each year

since 1960.

a) double b) was doubled c) has doubled

7. Micro-controlled cookers can be … for a variety of cooking tasks.

a) pre-programmed b) pre-program c) pre-programming

8. A natural language … constantly.

a) change b) is changing c) has changed

9. Though a programming language … in words, it can be used to

solve complex problems.

a) are limited b) limit c) is limited

10. Programming languages initially … by people in universities or in the

government.

a) were created b) had created c) has been created

11. The invention of high-level languages in 1950s … programming completely.

a) transform b) has transformed c) transformed

12. Data communication systems … gradually through the past two decades.

a) have been evolving b) have been evolved c) evolve

13. Most computer crimes … by accident.

a) discover b) is discovered c) are discovered

14. Public interest in the electric vehicle … higher by now.

a) become b) became c) has become

3.21. Complete the sentences with appropriate form of the verb given in brackets.

1. By the beginning of the lecture the lab assistant … all the necessary diagrams. (bring)

2. …. you … your diploma work yet? (complete)

3. The translation … yet. (finish). It … by the end of the month. (finish)

4. This problem … much in the press lately. (discuss)

5. This question … yesterday. (discuss)

6. The electronic industry … several types of microcomputers. (produce)

7. The air in many cities … by traffic and industry recently. (pollute)

8. The main drawback of our education is that it … practical training. (lack)

9. The necessity to develop an international ecological program … thoughout the world. (understand)

10. Our technological advances … to deal with the most difficult problems. (allow)

11. The new instruments … us to determine the level of pollution in our rivers in future. (enable)

12. Electricity has many useful properties: it is clean and … no by-products. (generate)

13. Who … the electric lamp? (invent)

14. The generator replaced batteries that … before. (use)

15. The consumption of electricity … every ten years. (double)