If only one professor was hired in 1991 then P was hired in another year: either 1990 or 1992.
A could be true, if P was hired in 1990. Then P wouldn’t be beside M. A is CORRECT.
B can never be true, even without the local rule. R and S are always beside each other.
C is wrong. One year after Orozco is 1991, and we know only one professor can be hired that year. R is already there.
D is wrong. No professor can ever be hired in 1994.
E is wrong. P can never be hired in 1993. Only M can be hired that year.
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