A doesn’t have to be true, since O could be hired in the same year as P: 1990.
B doesn’t have to be true, if P was hired in 1992.
C can’t be true. R is always in 1991 and S is always in 1992, after R.
D must be true. R is in 1991 and S is in 1992. D is CORRECT.
E can’t be true. M is in 1993 and S is in 1992.
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