Concept:Arranging persons left to right using given relative positions.Explanation:From "Q is left to R but right to P": P<Q<R.From "O is right to N and left to P": N<O<P.From "S is right to R and left to T": R<S<T.Combining all: N<O<P<Q<R<S<T.There are seven persons; the middle position is the 4th.The 4th person in this order is Q.Answer:Q