By saying that "Once the sands have run out of a persons hourglass, they cannot be replaced"(Lines 3-4, Paragraph 2), the writer means that
A. the sands that cannot be replaced will disappear.
B. the past time cannot come back again.
C. the hourglass cannot save time for people.
D. people should not wear hourglass with sands.
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The purpose of writing this text is probably to
A. praise the high technological level of Harvard Medical School.
B. comfort those patients who have developed coronary heart disease.
C. introduce a new therapy to cure heart disease.
D. criticize the traditional bypass surgery.
A foreigners first impression of the U. S. is that
A. fast-food industry in America is prosperous.
B. Americans are not polite in public eating-places.
C. Americans do not invite visitors to dinners to develop friendship.
D. Americans are often in a hurry to do things.
According to the text, the overindulgence of children refers to the
A. overabundance of toys and clothes.
B. generosity of parents being taken for granted by children.
C. expensive gifts that parents cannot afford.
D. excessive material possessions and privilegess.
结点级互联和主机级互联是通过中继系统实现网络互联的基本方法。()
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