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UID719480在线时间 小时注册时间2012-2-8最后登录1970-1-1主题帖子性别保密 
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| Questions 20-24 
 A lake contains exactly five islands-J, K, L, M, O-which are unconnected by
 bridges. Contractors will build a network of bridges that satisfies the
 following specifications:
 
 Each bridge directly connects exactly two islands with each other, and no
 two bridges intersect. No more than one bridge directly connects any two
 islands.
 
 No island has more than three bridges that directly connect it with other
 islands. J, K, and L are each directly connected by bridge with one or both
 of M and O. J is directly connected by bridge with exactly two islands.
 
 K is directly connected by bridge with exactly one island.
 
 A bridge directly connects J with O, and a bridge directly connects M with
 O.
 
 20. Which one of the following is a complete and accurate list of the
 islands any one of which could be directly connected by bridge with L?
 
 (A) J,K
 
 (B) J, M
 
 (C) J,O
 
 (D) J,M,O
 
 (E) J,K,M,O
 
 21. Which one of the following could be true about the completed network of
 bridges?
 
 (A) J is directly connected by bridge both with L and with M.
 
 (B) K is directly connected by bridge both with M and with O.
 
 (C) L is directly connected by bridge both with J and with M.
 
 (D) M is directly connected by bridge with J, with K, and with L.
 
 (E) O is directly connected by bridge with K, with L, and with M.
 
 22. If a bridge directly connects K with O, then which one of the following
 could be true?
 
 (A) No bridge directly connects L with M.
 
 (B) A bridge directly connects J with L.
 
 (C) A bridge directly connects L with O.
 
 (D) There are exactly three bridges directly connecting L with other
 islands.
 
 (E) There are exactly two bridges directly connecting O with other islands.
 
 23. If a bridge directly connects L with M and a bridge directly connects L
 with O, then which one of the following must be true?
 
 (A) A bridge directly connects J with M.
 
 (B) A bridge directly connects K with M.
 
 (C) A bridge directly connects K with O.
 
 (D) There are exactly two bridges directly connecting L with other islands.
 
 (E) There are exactly two bridges directly connecting M with other islands.
 
 24. If no island that is directly connected by bridge with M is also
 directly connected by bridge with O, then there must be a bridge directly
 connecting
 
 (A) J with L
 
 (B) J with M
 
 (C) K with O
 
 (D) L with M
 
 (E) L with O
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