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Инструкции к разделу 3.
В данном разделе вам предстоит прочитать текст, написанный в научном стиле. По прочтение этого текста вам нужно будет ответить на несколько вопросов, к каждому из которых предлагается 4 варианта ответов. Будьте внимательны - вам нужно выбрать не просто подходящий по смыслу вариант, а тот, который наиболее полно отвечает на поставленный вопрос.
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The appearance and the character of a hardened lava field depends on numerous factors. Among the key variables are the chemical nature of the magma and the degree of viscosity of the liquid rock once it begins to flow.
Since the ultimate nature of lavas is influenced by chemical compositions, it is possible to predict certain aspects of the final appearance of the field from a sample of molten fluid. The main components of lavas are silica and various oxides, including those of potassium, iron, calcium, magnesium, sodium, and aluminium. Magnesium and iron oxides are found in high concentrations in the dark-colored basic basalt, while silica, soda, and potash preponderate in the lighter-colored, acidic felsite rocks.
The viscosity of the liquid rock helps to determine the appearance of the hardened field's surface. When it issues, the lava is red or even white-hot. It soon begins to cool and the surface darkens and crusts over. In extremely viscous flows, the underpart may yet be in motion as the surface solidifies. The crust breaks up into a mass of jagged blocks of rock that are carried as a tumbling, jostling mass on the surface of the slowly moving stream. When eventually the stream stops and hardens, the field is extremely rough and difficult to traverse. On the other hand, highly liquid lavas may harden with much smoother surfaces that exhibit ropy, curved, wrinkled, and wavelike forms.
24. The degree of viscosity in newly issued lava is a critical determinant of:
25. The chemical composition of a hardened field:
26. In line 11, the word issue most nearly means:
27. Knots of surface rocks are characteristic of:
28. If the hardened lava presents a smoother, wavelike surface it is likely that:
29. The primary function of this passage is to:
30. The word exhibit in line 16 is closest in meaning to:
31. This passage would most likely appear in which type of publication?
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