单选题 Most teenagers in the United States try to make time for school , family and friends． But some choose bigger goals． Here are the stories of two American teens working to make a difference in the w

单选题 Poverty and the all-consuming worry that comes with it require so much mental energy that the poor have little brain power left to devote to other areas of life, according to the findings of an international study published on Thursday. Harvard economist SendhilMullainathan finds that the mental strain could be costing poor people up to 13 IQ (Intelligence Quotient) points, which means they are more likely to make mistakes and bad decisions that increase and keep their financial worries. 'The results suggest that when you are poor, money is not the only thing in short supply. Cognitive (认知的)capacity is also stretched thin,' he said. In a series of experiments, researchers from Harvard, Princeton and other universities in North America and from Britain's University of Warwick found that urgent financial worries had an immediate impact on poor people's ability to perform well in cognitive and logic tests. Far from signaling that poor people are stupid, the results suggest those living on a tight budget have their effective brain power, or what the researchers called 'mental bandwidth,' highly limited by the stress of making ends meet. On average, someone weighed down by money worries showed a drop in cognitive function in one part of the study that was comparable to a 13-point drop in IQ, and similar to the performance deficit expected from someone who has missed a whole night's sleep. 'Previous views of poverty have blamed it on personal failings, on an environment that is not helpful to success,' said Jiaying Zhao, an assistant professor of psychology. 'We are arguing that the lack of financial resources itself can lead to less active cognitive function,' she said. Professor EldarShafir said it was not stress in general, but financial worries in particular, that led to a reduced ability to make sound decisions. 'The poor are often highly effective at focusing on and dealing with urgent problems,' he said. 'But they don't have leftover bandwidth to devote to other tasks. So, if you live in poverty, you're more likely to make errors and errors cost you more dearly—it's hard to find a way out.'

单选题According to the author, by interacting with people who study liberal-arts, engineering students can______.

单选题By the end of this month we surely ______ a satisfactory solution to the problem.

单选题Bacteria are sometimes ______ too small to be seen without a microscope.

单选题Abruptly the ground fell away from our feet, and an ______ void opened before us.

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单选题只有李军知道怎样与她联系。

单选题I'm afraid I have no authority to ______ these documents to you.

单选题We develop trade with that company for our shared ______.

单选题Eager to see these celebrities, she ______ accepted the invitation to the party.

单选题The poor countries are extremely ______ to international economic fluctuations. A. inclined B. vulnerable C. attracted D. reduced

单选题It is __________ that text messaging while driving is dangerous.

单选题No other newspaper columnist has managed as yet to rival Ann Landers' popularity in terms of readership.

单选题The author regards George Mason's personal contribution to American law as ______. ( )

单选题There ______ little change in that middle school． A．have B．had C．have been D．has been

单选题The students do hope to _____ from the teacher’s comments on their compositions.

单选题At the beginning of the story, the fox seems to be all EXCEPT______.