This new rule changes everything. The limiting factor on the game was that 3 and 4 had to lecture about M and N. So nobody else could ever lecture about M and N. But now that 3 can lecture about S, then (for example) 4 could lecture about N. That lets 1 0r 2 lecture about M.
The possibilities are now quite open. Do not try to figure them all out, it’s wasted effort. Just try to get a feel for the new situation.
Since almost anything can happen, the only good way to violate a rule is to have 3 not lecture about S. If 3 doesn’t use the new option, then the game will work as before.
The new diagram looks like this. There are virtually no restrictions as long as 3 does choose S.
A could work, because 3 could lecture about S. (All of the wrong answers will have this same dull explanation.)
B doesn’t work because 4 can only lecture on M and N. This answer choices places M and N with other speakers. So 4 has no one left to lecture about.
B is CORRECT.
C doesn’t work, because 3 could lecture about S. That frees up M and N to be used elsewhere.
D doesn’t work, because 3 could lecture about S. That frees up N to go in 5.
E doesn’t work, because 3 could lecture about S. That frees up N to go in 2.
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