[单项选择]Possible Breakthrough in Renewable Energy
Plant scientists at the University of Michigan (150) an intriguing breakthrough. They are excited about a new breed of plant that can produce very high energy yields. The plant, which is a cross-breed of corn, wheat and barley, was originally made for another (151) .
The scientists were initially trying to develop a new feed crop for cattle. While the crop was a failure as cattle feed, additional testing showed that it had excellent biofuel properties.
Currently, the crop is in the experimental stage. Scientists need to do (152) work to determine under what conditions the plant grows best. This testing will be finished soon, and the plant should be out of the laboratory and in field trials by the end of the year.

A. make
B. had made
C. have made
D. would make

[单项选择]Possible Breakthrough in Renewable Energy
Plant scientists at the University of Michigan (150) an intriguing breakthrough. They are excited about a new breed of plant that can produce very high energy yields. The plant, which is a cross-breed of corn, wheat and barley, was originally made for another (151) .
The scientists were initially trying to develop a new feed crop for cattle. While the crop was a failure as cattle feed, additional testing showed that it had excellent biofuel properties.
Currently, the crop is in the experimental stage. Scientists need to do (152) work to determine under what conditions the plant grows best. This testing will be finished soon, and the plant should be out of the laboratory and in field trials by the end of the year.

A. option
B. purpose
C. extent
D. device

[单项选择]What’s the possible relationship between the two speakers
A. Husband and wife.
B. Doctor and patient.
C. Teacher and student.
D. Father and daughter.

[单项选择]
Scientists have been studying natural sources of methane for decades but hadn’t regarded plants as a producer, notes Frank Keppler, a geochemist at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. Now Keppler and his colleagues find that plants, from grasses to trees, may also be sources of the greenhouse gas. This is really surprising, because most scientists assumed that methane production requires an oxygen-free environment.
Previously, researchers had thought that it was impossible for plants to make significant amounts of the gas. They had assumed that microbes need to be in environments without oxygen to produce methane. Methane is a greenhouse gas, like carbon dioxide. Gases such as methane and carbon dioxide trap heat in Earth’s atmosphere and contribute to global warming.
In its experiments, Keppler’s team used sealed chambers that contained the same concentration of oxygen that Earth’s atm
A. The lower the temperature, the higher the amount of methane emissions.
B. Living plants release less methane than dried plants at the same temperature.
C. When exposed to sunlight, plants stop releasing methane.
D. The higher the temperature, the greater the amount of methane emissions.