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）
+ Q. I: ?6 E9 H　　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
0 G' `* S  p3 T" r6 t　　frigidly cold. But evidence is rapidly accumulating Mars was （6） __
5 a7 w2 A$ n% c1 p, |　　once much wetter， with a more clement climate. This evidence
  Q4 g; M; R: V; N: u( @　　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
/ \% W2 k& w% O: o4 L, w. a　　high-resolution imagery from the Mars Global Surveyor Mars
　　Orbiter Camera and the Mars Odyssey THEMIS reveal nu- （8） __
0 ~1 N2 W5 ?6 Y7 |" ^　　merous examples of branched valleys that form tightly-packed，
+ [9 c! X6 u3 }! N; m　　integrated drainage systems. These channels origins at topo- （9） __
7 `, G2 d, l% r2 h4 i　　graphic high points； the valleys widen “downstream”， some
, Q# R" A( P4 e　　even displaying inner valleys. The valley networks exhibit
1 [' D( D& b9 C8 k　　morphometric characteristics， including network densities，
( W# B! {3 N& y: A: A　　comparative to those of terrestrial drainage basins. These fea- （10） __
　　tures were most likely produced by rainfall， during wetter，
　　warmer periods in the past.