Put the verbs in brackets into their correct tense forms (present indefinite, present continuous, or present perfect).

1. Unit 9, which we just (complete), (demonstrate) the importance of straight thinking.

2. In the last few decades man (succeed) in utilizing the atomic nucleus as a source of energy.

3. At present, a number of research teams (look) for a new approach to the synthesis of proteins.

4. Many developing countries (retain) old and inefficient economic structures which (prevent) them from making the best use of modern agricultural and industrial methods.

5. The new machine, which (break down) several times recently (run) smoothly now.

6. Some types of steel (melt) at 1200⁰ C.

7. In the last few years, chemists (develop) hundreds of synthetic materials.

III.II.The The past perfectdescribes:

1. an activity that happened earlier than another activity in the past, e.g. Our studies showed how well the equipment had performed.

Notes:

To put emphasis on the duration of an action which started and finished in the past, before another past action or a stated time the past perfect continuousis used, e.g. He had been investigating genes for several years before he got positive results.

We use the past perfect tensewith these expressions: Before, after, till/until, when, by the time, never, etc.

Exercises

1. Put the verbs in brackets into their correct tense forms (past indefinite or past perfect).

1. Success (come) after we (perform) the experiment 20 times.

2. The engine (break down) before it (complete) all the reliability tests.

3. After the properties or characteristics of the new material (be worked out) theoretically, they (be tested) experimentally.

4. The field studies we (undertake) last year (be) very successful because they (be) carefully planned beforehand.

5. The construction of the bridge (begin) as soon as the engineers (make) the necessary calculations.

6. It (be) necessary to repeat the experiments because some of the original data (be lost).

7. Unfortunately, it (be) difficult to repeat the experiments since the original conditions (change) in the meantime.

2. Put the verbs in brackets in the following abstract into their correct tense forms (past indefinite or past perfect).

George E. Smith (receive) 2009 Nobel Prize in Physics – “For the invention of an imaging semiconductor circuit – the CCD sensor.”

I (be) born in White Plains, New York in 1930. I (attend) a variety of primary and secondary schools. After I (graduate) from high school I (join) the U.S. Navy. While (stay) in Miami, Florida, I (manage) to take enough courses at the University of Miami to qualify as a starting sophomore at the University of Pennsylvania in 1952. I (major) in Physics. After I (graduate) with honors I (marry). I (be) accepted into the graduate program at the University of Chicago with a job as a teaching assistant and (graduate) there in 1959 with a Ph.D. in Physics. During that time I also (receive) grants from the National Science Foundation and Bell Telephone Laboratories. As soon as I (graduate), I (be) offered a job with the Research area of Bell Labs and (accept) it.

Sentence translation

1. Freud divides human personality into three significant components: the id, ego, and super-ego. The id acts according to the pleasure principle, demanding immediate gratification of its needs regardless of external environment; the ego then must emerge in order to realistically meet the wishes and demands of the id in accordance with the outside world, adhering to the reality principle.

Finally, the superego (conscience) inculcates moral judgment and societal rules upon the ego, thus forcing the demands of the id to be met not only realistically but morally. The superego is the last function of the personality to develop, and is the embodiment of parental/social ideals established during childhood. According to Freud, personality is based on the dynamic interactions of these three components.

2. Light, the basis for all vision, is an element of our lives that we take for granted. We

are so familiar with brightness, darkness and the spectrum of visible colours that another form of perception in a different frequency range and with different colour sensitivity is difficult for us to imagine. Visible light is in fact just a small part of an essentially broader spectrum of electromagnetic waves, which range from cosmic rays to radio waves.

The first artificial light source was the flame of fire, in which glowing particles of

carbon produce light that, like sunlight, has a continuous spectrum. For a long time the production of light was based on this principle, e. g. flaming torches and kindling, the candle and the oil lamp and gas light.

In contrast to incandescent lamps, light from discharge lamps is not produced by

heating a filament, but by exciting gases or metal vapours. This is effected by applying voltage between two electrodes located in a discharge tube filled with inert gases or metal vapours.