When we buy a few gallons of petrol for out cars,we pay not only the cost of the petrol,but also part of the cost of the search that is always going on.

• 当我们为自己的汽车购买几加仑汽油时，我们付的不仅仅是汽油的价钱，而且还包括了一部分不断在进行着的勘探费用。