Problem # 31

This position arose after the following moves:
1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Bxc6 bxc6 5.0–0 d6 6.d4 f6 7.dxe5 fxe5 8.Nxe5 dxe5 9.Qh5+ Kd7? (diagram above).

This isn't the most difficult chess problem you'll come across, but how quickly can you determine White's best move?

Check your answer here.