When we exercise hard，we burn fat （脂肪）．But have you ever wondered where exactly the fat goes？
Some doctors think that fat is changed into heat and given off in the air．Others think the body burns it．Some even joke that someone comes and takes it．That's why you always weigh less in the morning．
Now a new study from Australia solves the mystery．
"The correct answer is that most of the fat is breathed out as CO2．It goes into thin air，"says the study．
Scientists followed the atoms （原子）in 10 kilograms of fat as they are lost．They found that 8.4 of those kilograms are breathed out as CO2 through the lungs （肺）．The other weight，1.6 kilograms，becomes water and leaves the body．
"None of this is easy to understand because we can't see the CO2 we breathe out，said the study's lead expert．
Does that mean you can lose more weight by breathing more？It is not as easy as you think．Breathing more than the body's metabolic rate （新陈代谢速度）can make you uncomfortable．You may feel dizzy （眩晕的）and become unable to see，move or feel，according to the study．
So how can people lose weight healthily？The key is to eat less and move more．You may have heard this many times．During a day．a 70kg person breathes out about 200g of CO2．So if the same person wants to lose weight，he or she can do some light exercise，for example，walking fast．This can help lose 24Og of CO2．
根据短文内容．选择圾佳答案．
（1）Where is the new study from？
A．Japan．
B．Australia．
C．Canada．
D．America．
（2）According to the new study，where does our fat go when we exercise a lot？
A．The body burns it．
B．Someone comes and takes it．
C．It is changed into heat and given off in the air．
D．Most of it is breathed out as CO2．
（3）What will happen to people if they breathe more than the body's metabolic rate？
A．They will lose weight healthily．
B．They will feel comfortable．
C．They may become unable to move．
D．They may becomc healthier．
（4）Which of the following is the best way to lose weight？
A．Sitting still and breathing more．
B．Sleeping a lot and breathing more．
C．Eating less and exercising more．
D．Eating more and doing some light exercise．
（5）The passage mainly tells us ．
A．where fat goes when we exercise
B．why we can lose weight healthily
C．how we should do some exercise
D．what we should do to burn fat．
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