11 almost all economists agree that nations, gain by trading with one another.
12 the conference explored the possibility of closer trade links.
13 the chemical is deadly to rats but safe to cattle
14 during his lifetime he was able to accumulate quite a fortune.
15 it's impolite to cut in when two persons are holding a conversation
b talk loudly
c stand up
答案11. b 12. b 13. a 14. c 15. d