Imagine you are a news photographer in the Middle East when a terrible flood strikes.

You set out in a boat with your camera to find a prize-winning picture, when you see Osama Bin Laden hanging from the branch of a tree.

"Help me", he calls. "I can't hold on any longer".

There is room in your boat, and if you don't help him he will drown.

You have a dilemma, and this is the question you have to answer:

What lens do you use?