Solution: From the meaning of the question, C+2 is included in A, so C is included in A-2, that is, C is included in {0,2,4,6,7}.

Similarly, C-2 is included in B, so C is included in B+2, that is, C is included in {3,4,5,7, 10}.

So c is included in {4 and 7}

So c should be {4}, {7}, or {4,7}.

I hope I can help you!