5. The primary source of energy ______ to the earth is the heat of the sun.
A: harmful
B: harmless
C: preferable
D: available
A: harmful
B: harmless
C: preferable
D: available
举一反三
- The sun basically provides Earth with_____ source of energy everyday. (limit)
- 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.
- Why does the earth become cool? A: Because the sun gives the heat to the earth. B: Because the moon gives the wind to the earth. C: Because the earth rotates . D: Because the sun's heat bounces to the space.
- The reason why all the solar energy falling on the earth can’t be utilized is that ______． 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
- Heat energy is a source of power， but （） will cause damage to the engine.