Table 10-3 presents an integer programming problem. Suppose you wish to add a constraint that stipulates that both alternative 2 and alternative 3 must be selected, or neither can be selected. How would this constraint be written?

A) X2 = X3
B) X2 ? X3
C) X2 ? X3
D) X2 + X3 = 1
E) None of the above

A