问题
选择题
分子、原子和离子都是构成物质的基本粒子。下列物质由原子构成的是[ ]
A．氯化钠
B．蒸馏水
C．氮气
D．金刚石
答案
答案：D
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分子、原子和离子都是构成物质的基本粒子。下列物质由原子构成的是[ ]
A．氯化钠
B．蒸馏水
C．氮气
D．金刚石
答案：D
| 阅读理解。 |
| Going to sleep may seem pretty boring compared with all the fun things you do while you are awake. But there's a lot going on in your mind and body while you are sleeping. Sleep, in fact, is as important to your survival as eating and drinking. Sleep improves your mood, makes you a better athlete, and helps you remember and understand what you learned during the day. During sleep, your temperature drops. Your heart beats slowly. A chemical that controls growth, which is called a hormone (荷尔蒙), moves into your bloodstream. Scientists think that sleep brings back energy and improves your immune (免疫) system. We know what happens while we're asleep because scientists study volunteers who sleep in laboratories. The sleepers are connected with machines that measure brain waves, eye movements and muscle activities. Sleep is like a school day: it's divided into different stages (阶段). When you are awake, your brain waves fire rapidly (迅速地). As you begin to relax and drift into the first stage of sleep, your brain produces slower-moving waves and you lose awareness (意识) of your surroundings. As you fall into deeper sleep, your body repairs itself from the normal wear and tear of daily life. Then, as you begin to drift back up to a lighter sleep, your mind becomes more alert (警觉的), and your dreams begin. You are in REM sleep. REM is the name for the rapid eye movement that happens while you are dreaming. During REM sleep, your eyes move back and forth behind your lids, as though you were watching a movie. During other stages, you might move in bed, but during REM sleep you're not making any movement. That's probably because if you could move, your body would act out your dreams. As you get close to morning, you spend more time in REM than in deep sleep, so you dream more. Researchers know that during REM sleep the part of the brain that deals with learning and thinking is very active. Getting too little sleep can affect your personality. Experts recommend that children get at least nine hours'sleep a night. |
| 1. Sleep has many advantages except _______. |
[ ] |
| A. improving your mood B. making you strong C. helping you study D. practising your eyes |
| 2. During your sleep, _______. ① your body repairs itself from the normal wear and tear of daily life ② your brain produces slower-moving waves ③ your dream begins ④ you lose awareness of surroundings Choose the right order: |
| A. ①③②④ B. ②④①③ C. ④①③② D. ④③①② |
| 3. Suppose this is the course of your sleep, in which part of the course do you have more dreams? |
[ ] |
| A. Light sleep. B. Deep sleep. C. REM sleep. D. The first two stages of sleep. |
| 4. Which of the following is NOT right? |
[ ] |
| A. During REM sleep, the whole brain is active. B. You don't move while you are in REM sleep, dreaming. C. The closer to morning, the more dreams you have. D. Hormone has something to do with your growth. |