Room 110 on the second floor is the _______ office. I know some of them.

1. A.
   doctors
2. B.
   doctor's
3. C.
   doctors'
4. D.
   doctors's

 Room 110 on the second floor is the _____ office. I know some of them.

A. doctors                B. doctor’s                    

C. doctors’                 D. doctors’s

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