mate in ... one

I have started to read Laszlo Polgar Chess: training in 5333+1 positions. It starts with 306 positions which are mate in one. I think this is a great way to practice the fundamentals. Any sportsman practice the basic movements of his sports hundreds of times a day. This set is the opportunity to really improve basic tactical vision, from the ground up. Here is one which really had me thinking (!)

white to move, mate in one.

I think this is one of the best ways to improve basic pattern recognition for beginner players.
 Have fun playing,