gwd1-16( 31套里的第一套第16题)

这道题我一点都不知道该怎么下手.可不可以给我解释一下这样的题应该怎么做.

1. Please always search for discussion threads before you post your question. 

http://forum.chasedream.com/dispbbs.asp?boardID=22&ID=176560&page=1

http://forum.chasedream.com/dispbbs.asp?boardID=22&ID=128922&page=1

2. Please always copy/paste the whole question because everyone has different versions of GWD.

Good luck studying, =)