What is the winning move...

... for White ?        Solution

From Winning Chess Exercises for Kids:

They say " Practice makes perfect,"
but that's only true when it is good
practice. So stay focused and play
seriously. Quick and sloppy games
will not help you improve. Consistent
accurate play is what to aim for.
It's best to practise with stronger
players or against someone just as
good as you. Nobody gets better by
beating up on easy opponents. They
let you get away with inferior moves.
You want a player who will see your
errors and force you to be sharp.