A: only a very small part is available
B: the sun is too distant from the earth
C: it takes thousands of years for this energy to be stored up in coal and oil
D: our scientific knowledge is not sufficient
举一反三
- The reason why all the solar energy falling on the earth can’t be utilized is that ______．
- Of the sun’ s total output of radiant energy, the earth receives （） A: one tenth B: one millionth C: all that comes from the surface of the sun D: a very small portion
- Quantity of energy contained in the atmosphere is ______. A: smaller than that in coal alone B: smaller than that either in oil or in gas that we have on Earth C: greater than that in coal, oil and gas on Earth combined D: greater than that in coal, oil and gas on Earth, respectively
- Why is more earth's heat blocked from escaping with more carbon dioxide in the atmosphere A: Carbon dioxide prevents the sun's energy from going back into space. B: Carbon dioxide radiates the sun's energy onto the earth. C: Carbon dioxide produces more heat in the atmosphere. D: Carbon dioxide takes in the sun's energy at infra-red wavelengths.
- 中国大学MOOC: The energy that the sun radiates to earth every is equivalent to the sum of all the fossil fuel energy of the energy.
内容
- 0
How much energy given off by the sun reaches the earth A: 100 % but indirectly B: 5 % C: 50 % D: only a very tiny amount
- 1
The energy that the sun radiates to earth every is equivalent to the sum of all the fossil fuel energy of the energy A: one day B: three days C: one months D: --
- 2
Why can’t people on earth be harmed by radiation A: We are too far away from any harm. B: We can protect ourselves. C: There is part of the atmosphere protecting us. D: There is special layers on our skin.
- 3
This passage centers mainly on ______ . A: harnessing energy through chemistry B: our last source of power C: how water power is produced D: the amount of solar energy that can be utilized
- 4
Solar panels, wind turbines, hydro power and geothermal energy and hydrocarbons (natural gas or coal) can all be used to produce hydrogen (a primary energy).