正确答案: A

《不要四面出击》

题目：1950年6月毛泽东在七届三中全会上作的重要讲话是

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学习资料的答案和解析：

[单选题]The subject of this passage is ________．

根据以下内容，回答下面的题目。Researchers have found that REM (rapid eye movement) sleep is important to human beings．This type of sleep generally occurs four or five times during one night of sleep lasting five minutes to forty minutes for each occurrence．The deeper a person’s sleep becomes, the longer the periods of rapid eye movement．There are physical charges in the body to show that a person has changed from NREM (non-rapid eye movement) to REM sleep．Breathing becomes faster, the heart rate increases, and, as the name implies, the eyes begin to move quickly．Accompanying these physical changes in the body is a very important characteristic of REM sleep．It is during REM sleep that a person dreams．According to the passage, how often does REM sleep occur in one night?

physical changes in the human body

[单选题]He ______ when the bus came to a sudden stop．

was almost hurt

[单选题]下列关于债权的说法，不正确的是 （　　）

债权具有排他性