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问题 单项选择题

心肌摄取201T1的量，主要与下列哪项因素有关（）

A.心肌厚度

B.缺血灶大小

C.冠脉血流量

D.心肌弥散性清除率

E.心肌细胞缺血时间

答案

参考答案：C

单项选择题

鞘氨醇的合成部位是

A．线粒体
B．胞液
C．内质网
D．溶酶体
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单项选择题

Questions 16～20


It is already common knowledge, on the beaches and in the cafes of mainland Europe, that Americans work too hard—just as it is well known on the other side of the Atlantic that Europeans, above all the French and the Germans, are slackers who could do with a bit of America’s vigorous work ethic.
But a new survey suggests that even those vacations American employees do take are rapidly vanishing, to the extent that 40 per cent of workers questioned at the start of the summer said they had no plans to take any holiday at all for the next six months, more than at any time since the late 1970s.
It is probably mere coincidence that George W. Bush, one of the few Americans who has been known to enjoy a French-style month off during August, cut back his holiday in Texas to a fortnight. But the survey by the Conference Board research group, along with other recent statistics, suggests an epidemic of overwork among ordinary Americans.
A quarter of people employed in the private sector in the US get no paid vacation at all, according to government figures. Unlike almost all other industrialized nations, including Britain, American employers do not have to give paid holidays.
The average American gets a little less than four weeks of paid time off, including public holidays, compared with 6.6 weeks in the UK—where the law requires a minimum of four weeks off for full-time workers—and 7.9weeks for Italy. One study showed that people employed by the US subsidiary of a London-based bank would have to work there for 10 years just to be entitled to the same vacation time as colleagues in Britain who has just started their jobs.
Even when they do take vacations, overworked Americans find it hard to switch off. One in three find not checking their email and voicemail more stressful than working, according to a study by the Travelocity website, while the traumas of travel take their own toll. "We commonly complain we need a vacation from our vacations," the author Po Bronson wrote recently. "We leave home tired; we come back exhausted "
Christian Schneider, a German-born scholar at the Wharton business school in Philadelphia, argues that there is "a tendency to really relax in Europe, to disengage from work. When an American finally does take those few days of vacation per year they are most likely to be in constant contact with the office. "
Mindful that well-rested workers are more productive than burnt-out ones, the accounting firm PricewaterhouseCoopers has started closing all its US offices completely twice a year, for 10 days over Christmas and about five around Independence Day. "We wanted to create an environment where people could walk away and not worry about missing a meeting, a conference call or 300 emails," Barbara Kraft, a partner at the company, told the New York Times.
Left to themselves, Americans fail to take an average of four days of their vacation entitlement—an annual national total of 574 million unclaimed days.

The author mentions George W. Bush cutting back his holiday to indicate that ______.

A. the tendency to overwork is limited to people holding important positions
B. ordinary Americans overwork and important ones are no exception
C. the president finds it necessary to cut back his holiday, let alone others
D. the president has every reason to overwork, but ordinary Americans don’t
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