题目

阿伏加德罗常数约为6.02×1023 mol－1，下列叙述正确的是(     ) A．36gH2O和22.4LCO2中Si和O，C和O之间的共价键均是4×6.02×1023 B．0.1 L 3 mol·L－1的NH4NO3溶液中含有的NH4＋数目为0.3×6.02×1023 C．常温常压下，4.6 g NO2气体含有0.1×6.02×1023个NO2分子 D．0.1 mol的甲基(—CH3)和羟基(—OH)所含电子数均为0.9×6.02×1023 答案：DDo you want to be healthier? Then go through the passage, and you may find it’s easy 1.fit.1).Eat all kinds of foods, especially fruits and vegetables.You may have a favourite kind of food, but the best 2.is to eat as many kinds as possible. If you eat 3. foods, you’re more likely to get the nutrients your body needs . Taste new foods that you 4. tried before. Some foods, such as green vegetables, are very important. Have five servings(份) of fruits and three vegetables.2)Drink water and milk often.When you are really 5.，cold water is the No. 1 choice. Kids need calcium(钙) to grow strong, and milk is a great source of this mineral (矿物质) . How much do children6.? About three glasses of milk every day.3) Limit screen time.What’s screen time? It’s the 7.for watching TV, DVDs, and videos, 8. computer games, and using the computer. If you spend much time 9. these activities, you may have less time left to take 10., such as playing basketball, bicycling, and swimming.