Q15

[ShehryarB30]

Could you pls explain this question

[ohthatpatrick]

If this question forces us to have M on 3 (and we always have M on 5), the next question should be ... where's the final M?

In this game, we mainly base our scenarios around whether the 3 M's are all together, or split up 2 and 1 (we learn early on that they can never be all split up).

If we wanted to make a 3-together scenario, we'd just have the three M's go 3/4/5

S S [] M M M [] S S

What can we get rid of from the answers?
(A) Eliminate. Our scenario is a counterexample
(B) Eliminate. Our scenario is a counterexample
(C) Eliminate. Our scenario is a counterexample
(D) Eliminate. Our scenario is a counterexample
(E) Pick it.

Weird. That was way too easy. For what it's worth, this "easy" scenario was actually the only possible scenario. Any other place that we put the 3rd M will create too many cleanings:
S S [] M [] S [] M M [] S
S [] M M [] S [] M [] S

(E) is really just rewarding the inference/observation we make that we never split up all three M's.

Since there's an M on 3 and an M on 5, and since we can't split up all three M's, it's impossible for there to be an M on 1. Thus, S is on 1.