Question

这是一道GRE逻辑题 拜托各路大神看一下吧

Neither the Sami nor the Kephrian delegations
attended the international conference. Beforehand. the
delegations of Daqua and Kephria. allies whose
governments had grievances against Tessia. officially
announced that one or both of the two would stay away
if the Tessian delegation attended the conference. In
response, the Sami delegation officially announced that
it would definitely attend if both the Daquan and
Kephrian delegations stayed away.

If the statements given are all true and all the
delegations adhered to their official announcements.
it must also be true that the

(A) Daquan delegation attended the conference

(B) Daquan delegation did not attend the conference

(C) Sami government had no grievance against
Tessia

(D) Tessian delegation did not attend the conference

(E) Tessian delegation made no official
announcement regarding its attendance at the
conference

本题的标答是E 哪位大神解释一下为什么A不对啊 跪谢~~~

Answer 1

符号说明：S,K,Da,T分别表示Sami参加，Kephrian参加，Daquan参加，Tessian参加；用“~”表示否定，“-->”表示蕴含，"&"表示并且，”v“表示或者。

由于题目问的是：
If the statements given are all true and all the delegations adhered to their official announcements, it must also be true that ...
就是要判断在假设【所有陈述都是真的】并且【所有代表团都忠实于他们的宣称】的情况下，下面的选项哪个是真的。

于是，从第一段的陈述中可以得知以下几点：

根据第一句话，
Neither the Sami nor the Kephrian delegations attended the international conference.
得知，
(1) ~S & ~K

根据第二句话，
Beforehand, the delegations of Daqua and Kephria, (allies whose governments had grievances against Tessia), officially announced that one or both of the two would stay away if the Tessian delegation attended the conference.
以及【所有代表团都忠实于他们的宣称】这个前提，得知，
(2) T --> (~Da v ~K)

根据第三句话，
In response, the Sami delegation officially announced that it would definitely attend if both the Daquan and Kephrian delegations stayed away.
以及【所有代表团都忠实于他们的宣称】这个前提，得知，

(3) (~Da & ~ K) --> S

根据p-->q与~p v q的等价性，可知(3)等价于 ~(~Da & ~K) v S；又由&和v的对偶性，可知(3)等价于，
(3') Da v K v S
由(1)和(3')就可以推出Da。

因此A是真的
B是假的，C、D、E真假不定。
标准答案是错的。

Answer 2

为了简便，用S,K,D,T代表4个代表团。现在的困惑是，A,B选项互相矛盾，根据排中律，肯定有一个对。但是结合实际情况会发现，D去的话可以没有理由，D不去是因为T去了，也可以是其他理由，因为题目并没有说信息是随时互通的，所以S去不去只能根据官方的宣告，而不能根据结果去推理，假设T去了，S根据宣告知道D和K至少有一个不去，但他并不能确定D和K能否同时不去，所以他去不去都可以，所有人只能等会议开始了才真正知道去了哪些人。
除非四国互派使者，每个代表团一出发就能被其他代表团知道，当作出不去的决定的时候也能被他国立即知道，否则只能根据官方宣告判断其他国去不去，而仅靠题目里的宣告根本推不出去或不去的，信息互通的话A就对了。
要我看的话，这道题目很复杂，但是选项很弱智，直接看到E选了就不用费脑子了，我们都想复杂了。

Answer 3

现在的情况是sami没有去，但是sami说了如果Daqua 和 Kephria都不去它就肯定去，所以Daqua和Kephria没有都不去←至少去了一个，但是没说是哪个，不一定是Daqua.
好吧我看错了。。其实是你拼错了吧，Kephria和Kephrian是同一个人？

追问

应该是指一个对象吧 只不过一个是名词一个是形容词 就跟Germany & German 或者 Spain & Spanish 一样 如果这样的话 题目中已说Kep没去 那Sam就一定去了啊 A即成立 你说是不是