Concept:If an element is in P∪Q but not in P, then that element must be in Q.Explanation:Given P={1,2,3,4,5} and P∪Q={1,2,3,4,5,6,7}.The elements 1,2,3,4,5 are already supplied by set P.The only remaining elements in the union are 6 and 7.Since 6∈/P and 7∈/P, they cannot come from P.Therefore, both 6 and 7 must belong to Q.The guaranteed elements of Q are {6,7}.This matches the correct option.Answer:Q={6,7}Option C.