Потому что действие на картине происходит прямо сейчас, симпл используется для описания регулярно повторяющегося действия, по картине нельзя сказать делают ли изображенные персонажи регулярно то, что они делают сейчас.
1. A small computer (hadn't been built) by 1974. 2. The first small computer (was build) by research engineer Ed Roberts in 1975. 3. Nearly two dozen patents (had been earned) by Doug Engelhart before he (introduced) the computer mouse. 4. Some people think that everything that can (be invented). 5. After the first Moving Assembly line (had been installed) Ford’s manufacturing principles (were adopted) by countless other industries. 6. Nylon (was invented) in 1983. 7. Though the first human heart (was transplanted) in 1967 a lot of experiments (had been carried out) ever since 1905. 8. People hope that new medicines (will be discovered) and dangerous diseases (will be cured).
1) Because it’s one of the most important sciences in the modern world. 2) Ecology helps us survive in the modern world. 3) People started speaking about ecology in the second part of the 20th century. 4) Ecology is closely connected with natural sciences such as biology, geography, phisics and so on 5) There are lot of problems ecologists are working on now: air pollution, water pollution, land pollution;shortage of natural resources;destruction of wildlife;the growth of population;traffic noise;acid rains;the greenhouse effect;global warming. 6) The environment can influence the growth of living things and the way they develop. For example: when we destroy forests various animals and birds die. 7) Human ecology studies the problems with nature which are connected with people. 8) My natural environment isn't healthy. People in my area take from nature as much as they can. They cut down forests and build farms, houses, roads on the land. While doing that, they pollute the environment. Cars and factories, plants and power stations also pollute the air and make it dangerous to breathe.
