相同质量的H2、CH4和CO完全燃烧需要氧气的质量[ ] A．CO最多，H2最少

One reason Americans eat so many calories is that we tend to eat large portions(分量). Studies find that hamburgers and fries are generally offered in serving sizes two to five times larger than the appropriate meal size. Researchers find we usually clean our plates no matter how high they're piled, even if we already feel satisfied. See the suggestions below to further master the fine art of sizing up（估量） your snacks and suppers.
Extremely large portions are one possible reason Americans continue getting fatter even as the percentage of our total calories from fat has gone down in recent years. Fortunately, portions are relatively simple to control because it's easier to count cookies than calories or grams of fat.
Pre-picture portions. Use familiar objects to picture how much you should eat of a food before you pick up your fork or spoon. For example, a half cup of low-fat granola is about the size of your fist. A half cup of low-fat ice cream equals half an orange.
Use a smaller dish. This tip might sound ridiculous, but it works. First and most obvious is that you can't put as much food on, say, a salad plate. But psychologically, you're just not as prone to eat as heartily and quickly if your plate will be empty in 45 seconds.
Have raw vegetables at every meal. Raw cucumbers, tomatoes, carrots, and peppers have few calories and lots of nutrients. A plate of them in the middle of the table almost always gets eaten up, cutting down appetite for the more calorie-dense meat.
Start your meal with soup. Studies show that a bowl of soup at the start of the meal reduces overall meal consumption, since they are lowest in calories and highest in nutrients.
Manage your fork. After every bite of food, put your fork down. Don't pick it up until you have thoroughly chewed and swallowed the previous bite. The goal is both to slow down your eating and to eat less. Remember: Your body needs 20 minutes of digestion before it sends signals to your brain that you are no longer hungry.

Helpful hints on how to get a handle on the how-much factor
Facts	Hamburgers and fries served in restaurants are generally two to five times the小题1:______of the proper ones. Americans usually clean their plates 小题2:______high they're piled, even if they are already satisfied
Effects	Americans continue getting fatter even as they have eaten小题3:______calories from fat in recent years.
小题4:______	a. Use小题5:______objects to imagine how much you should eat of a food before a meal. b. Use a smaller dish and thus eat 小题6:_____. c. Have raw vegetables at every meal to cut down 小题7:______    for the more calorie-dense meat. d. Start your meal with 小题8:______to reduce meal consumption. e. Put down your fork at小题9:______to make sure your brain receives小题10:______that you’re full.