Прочитайте текст Concrete is produced by combining coarse and fine aggregates Portland cement and wa...: ответ на тест 439326 - Английский язык

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Concrete is produced by combining coarse and fine aggregates, Portland cement, and water. Coarse aggregate is generally gravel or crushed stone, and fine aggregate is sand. Cement, sand, gravel and water are taken in proportional amounts and mixed. The quality of concrete depends mostly on the quality of the cement used. The process of production consists in pouring the mixed components into forms and holding them there until they harden. The process of hardening generally lasts for about 28 days.
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What does the quality of concrete depend on?

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Concrete is produced by combining coarse and fine aggregates, Portland cement, and water. Coarse aggregate is generally gravel or crushed stone, and fine aggregate is sand. Cement, sand, gravel, and water are taken in proportional amounts and mixed. The quality of concrete depends mostly on the quality of the cement used. The process of production consists in pouring the mixed components into forms and holding them there until they harden. The process of hardening generally lasts for about 28 days.
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What does the quality of concrete depend on?

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Aluminium, water, oxygen, and carbon dioxide are substances. Some substances are elements and some substances are compounds. Elements have only one type of atom whereas compounds have more than one type.
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How many types of atom do elements have?

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Boats on canal go through locks to move up or down from one level to another. The locks have large lock gates to let the boats in and out. They also have smaller sluice gates; these open and close to control the water level. The scale on the side shows the depth of the water in metres.
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What does the scale on the side of the lock show?

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Mrs. Sara Winchester of San Jose, California, was a very strange woman who built one of the world’s most unusual houses. When she died in 1922, aged 85, she was living alone in a house that had more than 150 rooms and covered an area of land greater than 2,5 hectares.
Mrs. Winchester’s problem was that she believed that if she stopped adding rooms to her house, she would die. Therefore, she employed workmen to keep on building and was happy only when she heard the sound of building. The house, when she bought it in 1884, was quite small, but 38 years later it was huge.
When she bought it, the house had two floors. By the time she died, it had eight. It had three lifts, 48 fireplaces and nine kitchens – none of which was ever used. In total, there were 2,000 doors and 10,000 windows. There were also miles of secret passages and tunnels that no one, not even Mrs. Winchester, knew how to get in to or out of.
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What was Mrs. Winchester’s problem?

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Alfred Nobel was a Swedish chemist who lived from 1833 to 1896. Alfred and his brother made explosives, but in 1864 there was an accident in the laboratory and Alfred’s brother was killed. Alfred then decided to spend his life truing to make explosives safer to use.
One of the strongest explosives at that time was nitroglycerine. This explosive, which looks like oily water, is very dangerous to use or even to carry. Nobel wanted to study nitroglycerine so he could find a way to make it safer. Nobel had an idea of taking nitroglycerine out on a boat in the middle of a lake and working with it there.
When Nobel wanted to take the nitroglycerine he was working with from one place to another, he put it into small boxes. Then he put the small boxes into a larger box made of clay. One day, when he opened the large clay box, he found that nitroglycerine was coming out of one of the small boxes. To his surprise, the large clay box was still dry. This gave him the idea of mixing clay with nitroglycerine. The clay would take the oil out of nitroglycerine and make it safer. He called this explosive ‘dynamite’.
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Why did Alfred decide to spend his life trying to make explosives safer to use?