单选题Please ______ from smoking until the airplane is airborne.

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单选题The economic recession has meant that job ______ is a rare thing.

单选题The tallest trees can be found ______

单选题Many people believe that our species ______ threatened with extinction.

单选题Social institutions are now being called ______ to provide assistance to the homeless.

单选题 Disagreement marks historical appraisals of America' s emergence as a great power at the turn of the twentieth century. On the one hand, historians have praised the maturing of the Republic, which was now able to take its place among the arbiters of the world' s destinies. On the other hand, many writers have tried to define America' s new floe indistinctive terms. They argue that the United States did not enter the great power game as just another player but introduced a new style of diplomatic play and perhaps even a new set of rules. Judgments clash about these innovations. An older school of thought stresses the idealism that America brought to the world arena. More recently, "New left" revisionists have charged that America' s contribution to international life was the self-serving notion of "informal empire," typified by a worldwide Open Door doctrine. This strategy avoided formal territorial possession but sought economic dominance of foreign raw materials, markets, and investments. Historians disagree further about the motivating impulses of American diplomacy. Recent "revisionists" have tended almost exclusively to emphasize domestic economic factors in explaining American foreign policy, the United States sought foreign markets, the argument goes, to solve the problems of domestic overproduction and constant business depressions. Other scholars respond that international politics can only be properly understood in an international con- text. They argue that Theodore Roosevelt, for example, acted not for narrow domestic reasons but because he realistically perceived that if the United States did not hold its own against the other powers, it would soon risk being eclipsed on the world stage, and even being pushed around in its own hemisphere, despite the Monroe Doctrine.

单选题Time was ______ you could buy a loaf of bread for sixpence.

单选题There is no doubt ______ the couple did the right thing in coming back home earlier than planned.A. whetherB. thatC. whyD. when

单选题Why did some 'IT practitioners agree to be the subjects of Emily's experiment?

单选题 {{I}} Questions 7 to 10 are based on the following conversation. At the end of the conversation, you will be given 20 seconds to answer the questions. Now listen to the conversation.{{/I}}

单选题When she graduated from the best high school in that city, she got her______.A. diplomatB. certificateC. degreeD. identity

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单选题 {{I}} Questions 29 and 30 are based on the following news. At the end of the news item, you will be given 10 seconds to answer the questions. Now, listen to the news.{{/I}}

单选题Western Nebraska generally receives less snow than ______ eastern Nebraska.