In 1960—1961, Chad had a good harvest of cotton because______.

A:the government greatly encouraged peasants B:rains favored the growth of cotton C:Chad gained independence in the previous year D:both A and B

______ they will have a good harvest this year is still unknown.

A:Whether B:If C:Which D:That

（　） a holiday, we went to the farm to help the farmers with their harvest.

A:Being B:It being C:Having been D:It was

The harvest this year is ______ by too much rain.

A:influenced B:effected C:affected D:interfered

Studies of deforestation(采伐森林，毁坏森林) in Amazon rainforest have underestimated the actual extent of forest loss by half or more, according to a study published in the April 8, 1999, issue of the journal Nature.
Past efforts to estimate deforestation in the Amazon have relied on satellite images to calculate forest loss. The new analysis found that satellite images were useful for estimating deforestation by logging(伐木)and fires on an extent of land, but failed to capture numerous smaller pockets of damage, including damages caused by selective logging(a harvesting technique in which only selected trees are removed) and surface fires, which is often hard to detect from satellite images, as new growth quickly masks it.
The new study focused on Brazil’s Amazon region, where most of the rainforest is located. The researchers interviewed 1,500 wood mill operators and 200 landowners about logging practices, harvest records and fire damages on their lands. The researchers verified the information collected by measuring the actual wood harvest in selected parts of forest, and by surveying fire damages from an airplane at over 1,100 sample points.
The research team found that damage from the fires varied significantly from year to year due to larger environmental factors, but roughly similar damage caused by logging. They determined that actual deforestation in the Brazilian Amazon was at least double the damage estimates derived from satellite images.
Damages caused by logging and fires threatened the Amazon rainforest. Sunlight can penetrate holes in the forest shelter and reach the floor, drying plants and increasing the risk of fire. At the global level, many scientists worry that continued burning and logging in the forest will further raise levels of carbon dioxide in the atmosphere. Rising levels of carbon dioxide—a so-called greenhouse gas because it traps heat in the lower atmosphere— has been linked to global warming.
Strict limits on logging, stronger efforts preventing fire, and controls on development could all help slow deforestation, the researchers said.

A:Interviewing wood mill operators and landowners about logging. B:Surveying fire damages from the airplane. C:Measuring the actual wood harvest in selected parts of forest. D:Surveying the damage of forest caused by Amazon floo

Because of the poor harvest, wheat prices have ______ in the last six months.

A:added B:jumped C:amounted D:developed

______ they will have a good harvest this year is still unknown.

A:Whether B:If C:Which D:That

The harvest this year is ______ by too much rain.

A:influenced B:effected C:affected D:interfered