Today's Geo Quiz takes on a subject that makes a lot of us uncomfortable. It's something we'd rather not talk about in public. No, it's not sex. It's not religion. It's...the price of energy.

The more squeamish among you might want to leave the room at this point. But the fact is that oil is selling for almost 134 dollars a barrel. And natural gas is plenty expensive, too. The impact on the US economy and consumer confidence has been significant.

But consider this. In some countries, the key energy source isn't oil or gas.

It's wood, straw, or manure.

Foreign Policy magazine put this question to its readers: How many people in the world meet their energy needs with one of those three -- wood, straw, or manure?

And now we're asking you: Is it 1 million, 2 1/2 billion, or closer to 4 billion?

Try to make a guesstimate.