Ⅰ、1-5 DCBAD
6-10 BCDDC
11-15 CACBB
16-20 DBDAC
Ⅱ、 21-25 BADAC
26-30 ACBCD
Ⅲ、31-35 CDCBA
36-40 BABCD
Ⅳ、41-45 DCAFB
Ⅴ、 46、population
47、crowded
48、pills
49、 dried
50、specially
51、have visited
52、 cutting
53、is
54、 having
55、feel
Ⅵ、56、in
57、directed by
58、because of
59、How; like
60、it difficult
Ⅶ、61、future
62、 different
63、even
64、 fewer
65、Travelling
66、changes
67、expensive
68、vegetables
69、healthier
70、 problem
Ⅷ、 One possible version:
Dear Jim:
Now,I'm writing a letter to you on Mars. It's really wonderful to live on Mars. I think life on Mars is more comfortable and more interesting than on Earth. We have online schools instead of real ones. We do our homework, take exams and talk to teachers and classmates through an interplanetary computer network at home. Most of our housework is done by robots so that we can have more time for our hobbies. Mars is very beautiful. There are green trees and fresh flowers every,Arhere, and there is no pollution here.We have supermarkets in our neighborhood.They make our life more convenient.
Yours,
Kate