英语专八考前自测冲刺题：改错下

会计考友

　　Mars has provoked much speculation on the possibili- （1）
　　ties of life beyond Earth than any planet in the Solar System. （2） __
5 ?; \) o) S7 A' G  i8 d* o2 I　　The presence of water is a prerequisite for the existing of life. （3） __
: P/ @# h0 f, t5 e8 V, w　　Therefore， “follow the water” has been NASA' s chief guide-
: T  R  J  L3 j: K　　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） __
1 Z9 g7 w  i4 a  Y8 S& D　　once much wetter， with a more clement climate. This evidence
　　comes from orbiting satellites and from data collected by rov-
　　ing landers.
! ^/ z: D0 J- V7 `# A3 [　　Since 1970s， space probes to Mars have revealed numer- （7） __
' F+ R1 v1 @; _　　ous features apparent carved by flowing water， such as wind-
　　Lng， branched valleys resembling dried-out streambeds and gi-
  F5 C/ [- ]4 g　　ant outflow channels gouged by catastrophic floods. Recent
　　high-resolution imagery from the Mars Global Surveyor Mars
: e6 j) ]: ]& g# b　　Orbiter Camera and the Mars Odyssey THEMIS reveal nu- （8） __
! S- Q) g* ~' j. T/ K/ v) D　　merous examples of branched valleys that form tightly-packed，
& b3 c& G, \4 X$ {! V　　integrated drainage systems. These channels origins at topo- （9） __
　　graphic high points； the valleys widen “downstream”， some
/ t! ]$ Z% m" ]1 q  B0 w　　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.