If n is a positive integer, which of the following expressions must be even?  Pick:  A) (n − 1)( n + 3)  B) (n − 6)( n + 1)  C) (n − 2)( n + 6)  D) (n − 3)( n + 3)  E) (n − 3)( n + 7)
Whether n is even or odd, (n-6)(n+1) will have one odd factor and one even factor.   The product will be even.   The answer is (n − 6)( n + 1).
<result>B</result>
If n is a positive integer, which of the following expressions must be even?