¡¡¡¡70.It is amatter of common observation that a body A cannot exert force on a second body B without B at the same time exerting force on A.
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¡¡¡¡71.Without the sun's light warming the earth's surface£¬it would be so terribly cold that life¡¡could not exist.
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¡¡¡¡72.Just as the length and cross-section of the pipe affect the flow of water so it is with conductors of electric current.
¡¡¡¡ÕýÈç¹ÜµÀµÄ³¤¶ÈºÍ½ØÃæ»áÓ°ÏìË®Á÷Ò»Ñù£¬µ¼Ìå¶ÔµçÁ÷µÄÓ°ÏìÒ²ÊÇÈç´Ë¡££¨with±íʾ¹ØϵºÍ·¶Î§£¬ÓС°¹ØÓÚ¡±£¬¡°¶Ô¡±£¬¡°¾Í¡±Ö®Òâ¡££©
¡¡¡¡73.Water vapor may vary from almost nothing to as much as 4£¥ and is not usually included¡¡with the other constituents which£¬in terms of global averages£¬do not vary significantly.
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¡¡¡¡74.This atom£¬with 92 electrons spinning about the closely packed and complex nucleus£¬is the element uranium£¬which seems to be the most complicated of the natural atoms.
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