LSAT-6-4-20-24(lawyer改标题)

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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 islands 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 exacly 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.

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 direcdtly connecting

A) J with L

B) J with M

C) K with O

D) L with M

E) L with O

lawyer_1

画图

条件：1。每个到最多和三个桥连。2。J，K，L至少和M,O中的一个连。3。J连2条桥。4。K连1条桥。5。J和O连，M和O连

21。A导致L连接3个桥，错。B错。D导致M连4条桥，错。E导致连4条桥，错。剩下C为答案

22。A因为L不能和O连，所以只能和M连，错。C导致O有4条桥，错。D.L只能和J，M，不能和OK连，所以不可能有3条桥和L连，错。E.O和条桥连，错。剩下B为答案

23。由于O已经和JLM连，故不能和K连，故K必须和M连。B对

24。由于JM不能连，故J只能和L连。A对

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昨天大概脑子有问题了，这么简单的题啊没做出来。thank you lawyer_1