题目内容：

    One of the questions surrounding climate change is how it might affect the food supply for a growing global population. A new study suggests that researchers have been overlooking how two key human responses to climate—how much land people choose to farm, and the number of crops they plant—will affect food production in the future. The new study focused on the Brazilian state of Mato Grosso, an emerging（新兴的）global breadbasket（产粮地区）that as of 2013 supplied 10 percent of the world’s soybeans. The researchers used variations in temperature and precipitation（降水）across the state over an eight-year period to estimate the sensitivity of the region’s agricultural production to climate change. Those historical comparisons can help in making predictions about the sensitivity of agriculture to future climate change.

The study found that, if the patterns from 2002 to 2008 hold in the future, an increase in average temperature in Mato Grosso of just 1 degree will lead to a 9 to 13 percent reduction in overall production of soy and corn. “This is worrisome given that the temperature in the study region is predicted to rise by 2 degrees by 2050,” said Avery Cohn, who led the study.

Most studies of this kind look only at the extent to which climate shocks affect crop output. But researchers can miss critical dynamics（动力）that can affect overall output, says Leah VanWey, one of the study’s senior authors. “If you look at output alone, you’re not looking at all of the information because there are economic and social changes going on as well,” said VanWey.

If output decreases, farmers may put less land area into production because it’s not profitable. Farmers may also vary the number of crops they plant in a growing season. Double cropping is common in Mato Grosso. But if the weather is bad, farmers may change their decision to plant a second crop.

1.The value of the new study lies in _________.

A.increasing the number of crops people plant

B.focusing on an emerging global breadbasket

C.making predictions about human responses to climate change

D.controlling people’s choice of their farming area and crop numbers

2.According to Avery Cohn, by 2050, the overall production of soy and corn will _________.

A.remain almost unchanged B.decrease by more than 9%

C.increase by from 9% to 13% D.decrease by more than 18%

3.What can we know about the similar studies mentioned in paragraph 3?

A.They can’t provide exact information to farmers.

B.They don’t take into consideration some key factors.

C.Their discouraging results largely affect overall crop output.

D.They pay too much attention to economic and social changes.

4.What is the last paragraph mainly about?

A.Farmers’ possible reactions to climate shocks.

B.Possible climate change in Mato Grosso.

C.The benefits of double cropping in Mato Grosso.

D.Farmers’ decision on planting crops in the future.