单项选择题

Cosmos 2251 was an ordinary satellite designed to transmit signals across the vast Russian landmass. Launched in 1993, it would appear every 90 minutes or so over the northern skies, relay electronic blips of information among a network of satellites and ground stations like a hockey player passing the puck (冰球运动中当球用的橡胶圆盘), and disappear over the southern horizon.
Cosmos was designed to

A. play hockey with human players.
B. guard the Russian landmass.
C. patrol over the Russian sky.
D. send information back to stations.
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Now, however, armed with brain-scanning tools and a sophisticated understanding of biochemistry, researchers are realizing that the mental effects of exercise are far more profound and complex than they once thought. The process starts in the muscles. Every time a bicep (二头肌) or quad contracts and releases, it sends out chemicals, including a protein called IGF-1 that travels through the bloodstream, across the blood-brain barrier and into the brain itself. There, IGF-1 takes on the role of foreman(工头, 领班)in the body’s neurotransmitter factory. It issues orders to ramp up production of several chemicals, including one called brain-derived neurotrophic factor, or BDNF. Ratey, author of the upcoming book Spark: The Revolutionary New Science of Exercise and the Brain. calls this molecule Miracle-Gro for the brain. It fuels almost all the activities that lead to higher thought. The process of exercise functioning on mind starts
A. in the muscles.
B. in the bloodstreams.
C. in the brain.
D. in the heart.
单项选择题
This doesn’t mean that wind and solar, which currently provide less than 1 percent of the world’s primary energy, will replace fossil fuels, which provide 82 percent. In fact, while companies like BP and Shell are cutting back on commercial projects in wind and solar, Big Oil is taking a closer look at how they might be used to increase efficiency internally, or to flee up increasingly profitable fossil fuels, like natural gas, for commercial sale. For example. Valero is building windmills to power refineries, and Chevron is using solar power to make steam to extract tough-to-reach oil. When you consider that the top 15 oil and gas companies have a market capitalization of $1.9 trillion, it’s clear that these firms themselves have the potential to be major renewable customers. Big oil is thinking of using wind and solar
A. to free up fossil fuels for commercial sale.
B. to replace fossil fuels for commercial sale.
C. to increase efficiency of fossil fuels use.
D. to reduce harm to the environment.
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