题目内容：

John Davis doesn’t use his GPS system in his car. Instead of guiding the direction, the Delaware farmer uses it to determine where and how much fertilizer to use on the crops on his 4,000-acre family-owned farm. Technological advances like that last year helped Davis and other Ohio farmers set a record for corn product. Ohio's corn crop in 2009 totaled 546 million bushels(蒲式耳), despite a cooler and wetter than normal spring, a dry summer and a delayed, wet harvest. Davis said. “I knew it would be a good crop, but it was much better than we expected.”

A farmer can map his fields on GPS, spotting where soil turned out to be least fertile（肥沃的） and using more fertilizer the next year in those areas where corn didn’t grow as well.

Although Ohio farmers produced more corn, it was grown on less land than in the past years. Total area used for corn in Ohio was 3.35 million acres, about the same as in 2008 but down from 3.85 million acres in 2007, said Dwayne Siekman, director of the Ohio Corn Growers Association. “When you look at the total number of acres in Ohio used for corn, it’s clear that farmers are able to do more with less,” he said. “American farmers can grow five times more corn on 20 percent less land than they did in the 1930s, saying that modern farming techniques are necessary for a growing demand in the world today.” That technology includes using improved seeds that can withstand(忍受) greater temperature extremes and pests, Siekman said.

Farmers aren't the only ones who benefit. Consumers(消费者) do, too, as food costs reduce in the face of “enough supplies of corn,” said Fred Yoder, who runs a 1,500-acre corn, soybean and wheat farm in Plain City. “This is the best, highest-producing corn crop that I've raised in 30 years,” he said.

1.Most people usually use the GPS system for ______.

A. driving their cars

B. telling the position

C. mending the car

D. supplying the sunshine

2.The farmers in Ohio use GPS to ______.

A. check if the soil is fertile in some areas

B. control the rain of the place

C. water the crops if the weather is dry

D. draw the map of all the crops

3.Why did Ohio farmers produce more corn?

A. Because they expanded more land to grow corn

B. Because they turned to technological advances

C. Because they used more and more fertilizer.

D. Because they supplies themselves with more money.

4. From the passage, we can know _____.[

A. John Davis hadn’t expected a good harvest.

B. farmers grew less land than in the 1930s

C. improved seeds cost much more money

D. the output of corn in the same field is increased.