>>512
英 mathoverflowで>>512関連
http://mathoverflow.net/questions/152787/can-an-infinite-number-of-mathematicians-guess-the-number-in-a-box-with-only-one
Can an infinite number of mathematicians guess the number in a box with only one error? - MathOverflow edited Dec 26 '13 user44653
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In this question＊） the following observation was made:
＊）上記 Probabilities in a riddle involving axiom of choice - MathOverflow: edited Dec 9 '13 Denis mathoverflow にリンクされている

Consider a sequence of boxes numbered 0, 1, ... each containing one real number. The real number cannot be seen unless the box is opened.
Define a play to be a series of steps followed by a guess. A step opens a set of boxes. A guess guesses the contents of an unopened box. A strategy is a rule that determines the steps and guess in a play, where each step or guess depends only on the values of the previously opened boxes of that play.
Then for every positive integer k , there is a set S of k strategies such that, for any sequence of (closed) boxes, there is at at most one strategy in S that guesses incorrectly.

My question is this: Can k be countably infinite (instead of a positive integer)? If not, is there a proof?

[Edit: the original question also asked whether k can be uncountable; this was answered by Dan Turetsky in the negative in comments].
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