题干

吸烟有害健康,科学实验表明香烟所产生的烟雾中,至少有300多种化合物不同程度对人体有害.为了检验该烟雾中是否存在CO2和CO,在对香烟燃烧产生的烟雾进行适当处理后,依次通过足量的以下试剂:①澄清石灰水,②浓硫酸;③灼热的黑色氧化铜粉末,④澄清石灰水,发现①、④变浑浊.试回答:
上一题 下一题 0.0难度 选择题 更新时间:2019-07-25 04:00:47

答案(点此获取答案解析)

同类题3

阅读理解

    One of the main decisions you must make when traveling is deciding where to stay. A place to stay can often make or break a holiday. Whether you are looking for a classy hotel or a night under the stars, we can guide you through your different options.

    Bed and Breakfast

    An English invention, bed and breakfasts, offers exactly what they suggest, a bed for the night and breakfast in the morning. “B&Bs”,are usually someone's private home, often found in the countryside.

    Hostels

    For those traveling on a tight budget, hostels are the best accommodation option. Informal places usually with a lovely relaxed atmosphere, they offer dormitory beds for rent. Bathrooms are usually down the hall.

    Remember to check reviews by previous guests online before you book your hostel.

    Couch Surfing

    An unusual but interesting option, couch(沙发) surfing is a growing trend among young internationals. The idea is that you become a member of the online couch-surfing community (www. couchsurfing. com) and then when you travel, look up other members in that country and ask to stay on their couch. Most hosts will suggest sightseeing trips and take you out in the evening, making it a great way to see things that aren't in your guidebook. And remember, it may be free but don't forget to offer to buy your host a drink or dinner.

    Camping

    Sleeping under the stars! For budget travelers staying at camping grounds is the cheapest way to travel. The drawback is having to carry a tent with you. Camping grounds can be found across Europe, America and Australia. However, if you intend on camping in busy cities check first where the nearest place for camping is. More often than not, they are on the edge of cities, which can mean lengthy bus rides into town when you want to eat or see the sights.