A、The world economy is booming. B、There was more demand than supply. C、There was more supply than demand. D、Oil production was r

Crude oil is measured in barrels. [5]Last summer, its global price was $100 per barrel. Yesterday, it was trading at less than half of that, at about $46.50 a barrel.
    Why does that matter? Well, the price of crude affects everything from gas prices to car prices, to stock prices. And it determines the number of jobs in the large global oil industry. [6]The current surplus of oil gives us a clear lesson in the economic principle of supply and demand. When it comes to oil, it used to be all about the Middle East. Today, the Persian Gulf still has plenty of crude, but the boom is global. We produced a surplus of 2 million to 3 million barrels per day.
    [7]Oil buried deep beneath the earth surface in rock can now be accessed with new technologies like tracking and horizontal chilling. Two years ago, U.S. oil production saw its biggest jump in more than 100 years, and it’s not the only country to gain a large flood of crude. Production in Canada and Brazil has also hit record levels. At the same time, there are more alternatives to oil, like natural gas and renewables. When oil supply exceeds demand, prices fall.
5. What happened to oil price?
6. What caused the change of oil price?
7. Why does oil production increase dramatically?