GokyoShumyoSection4Problem16/Solution

White wins  

is the only correct move. here is inferior.

Solution: Ko  

Black should choose the other 1-2 point. and make ko ( at a loses to at ). (Against this small box shape, the 1-2 point nearer to your weaker string is usually the better choice because it threatens to connect underneath and increase the liberties. Compare the two diagrams)