Life on earth depends on the sun. Day after day we see its light and feel i

游客2023-09-08  23

问题      Life on earth depends on the sun. Day after day we see its light and feel its【B1】______ , but we do not often know or【B2】______ the birth or the beginning of their【B3】______ . Yet there are amount of【B4】______ things about the sun. One is its distance from the earth. This is about ninety-three【B5】______ miles. It is to us, a long distance. A【B6】______ of this distance, even if it could be made, would take【B7】______ hundred years even in the【B8】______ rocket.
     The sun makes us feel heat, even at a distance of ninety-three million miles. This is not surprising.【B9】______ . But we receive only a small part of this heat. The total heat of the sun could melt a column of ice two and a quarter miles thick and ninety-three million miles high in one second.
    The brightness of the sun is equally astonishing. As we said earlier, we receive only a very small part of the sun’s heat.【B10】______ This is sufficient for the growth of trees and plants, and for the existence of living creatures on earth.【B11】______ . The heat and light from the sun come in just the right quantities for life on earth. [br] 【B7】

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