Oh, come on. It's easy enough to figure out! It's always the other button, as in not the one labeled Cancel. Or No. Rarely, Reject/Fail/Abort. Except when there

Oh, come on. It's easy enough to figure out! It's always the other button, as in not the one labeled Cancel. Or No. Rarely, Reject/Fail/Abort. Except when there's only one button, then you use the X in the corner. If it's there. What could be simpler?