又是一道逻辑求解

taoransk

Eight Olympic sprinters ran100 meter dash and finished in following order:
　　A finished before B
　　F finished before Evan
　　Bill finished before Charles
　　Dave finished after Charlesand B
　　Ham finished after G
　　Evan finished before Charles and D
　　G finished After B




　　Q2. If Ham finishes after Chaeles, then now howmany runner must finish before Chaeles?
　　A. 2.
　　B. 3.
　　C. 4
　　D. 5.
　　E 6




答案是c=4
问题在于, 由提示1&3推出A&B 在C前, 由提示2&6推出F&E在C前,
然后由提示5得到G在H前,而题目前提定的是C在H前,那么可能出现的情况是FEABGCHD啊,那么C前面应该是5个才对.....

读了几遍,也没有说所有before/after是一个紧贴一个的?



然后在解释里是这么一段we can see only H abd D after C, so that the answer is C: there would be 4 eunners finish before C.
这个...如果only H&D after C,那么8个人, C是第6个,前面应该有5个来着...


原题在这里http://www.qnr.cn/waiyu/lsat/fudao/200910/218829.html

taoransk

等了灰常多天了