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当膈肌收缩时( ) A.膈肌顶部上升B.胸廓容积缩小C.肺内气压增大D.气体进入肺内
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I ________ through that bitter period without your generous help.
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The teacher has told us something _____ we should do in the summer holiday.
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In order to protect the environment, people are greatly encouraged to travel by public ____. [ ]
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学校举行运动会,小刚参加了跳远比赛项目。想一想,怎样测量比较准确?
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