英语专八考前自测冲刺改错题2_TEM8试题

    mars has provoked much speculation on the possibili- (1)
    ties of life beyond earth than any planet in the solar system. (2) __
    the presence of water is a prerequisite for the existing of life. (3) __
    therefore, "follow the water" has been nasa' s chief guide-
    line for the exploration of a red planet. although mars experi- (4)
    ences seasons like on earth and has polar caps which com- (5) __
    posed of carbon dioxide and water ice, today it is bone-dry and
    frigidly cold. but evidence is rapidly accumulating mars was (6) __
    once much wetter, with a more clement climate. this evidence
    comes from orbiting satellites and from data collected by rov-
    ing landers.
    since 1970s, space probes to mars have revealed numer- (7) __
    ous features apparent carved by flowing water, such as wind-
    lng, branched valleys resembling dried-out streambeds and gi-
    ant outflow channels gouged by catastrophic floods. recent
    high-resolution imagery from the mars global surveyor mars
    orbiter camera and the mars odyssey themis reveal nu- (8) __
    merous examples of branched valleys that form tightly-packed,
    integrated drainage systems. these channels origins at topo- (9) __
    graphic high points; the valleys widen "downstream", some
    even displaying inner valleys. the valley networks exhibit
    morphometric characteristics, including network densities,
    comparative to those of terrestrial drainage basins. these fea- (10) __
    tures were most likely produced by rainfall, during wetter,
    warmer periods in the past.