18．Bad breath can be a major problem．The good news is that it can often be prevented with some simple steps．
Bad breath is caused by certain bacteria that grow in the mouth．When you don't brush regularly，bacteria accumulate in your mouth and between your teeth．（36）ACertain foods，especially ones like garlic and onions that contain pungent （辛辣的）oils，can contribute to bad breath because the oils are carried to your lungs and out through your mouth．（37）CSome people think that as long as you brush your teeth，you shouldn't have bad breath． （38）EThat，however，just doesn't remove the smell．To sufficiently clean all the surfaces of your teeth，you should brush for at least 2minutes at least twice a day．
Many people believe that if you breathe into your hand，you'll know when you have bad breath．But it's wrong!（39）G3When you talk，you tend to bring out the smell from the back of your mouth （where bad breath starts），which simply breathing doesn't do．Also，because we tend to get used to our own smells，it's hard for a person to tell if he or she has bad breath．
If you're concerned about bad breath，make sure you're taking care of your teeth and mouth properly．If you brush properly and visit your dentist for regular cleanings but your bad breath persists，you may have a medical problem．（40）BThey can figure out if something else is behind your bad breath and help you take care of it．
A．These bacteria make your breath smell．
B．In that case，call your doctor or dentist．
C．Smoking is also a major cause of bad breath．
D．Remember to brush your tongue，too-bacteria love to hang out there．
E．The truth is that most people only brush their teeth for 30to 45seconds．
F．When you breathe，the smell bounced back by your hand can be easily sensed．
G．When you breathe，you don^use your throat the same way you do when you talk．
分析 短文主要讲了口气是如何产生的，以及如何解决这问题．
解答 36．A，考查前后衔接，前文提到When you don't brush regularly，bacteria accumulate in your mouth and between your teeth，如果不定期刷牙，就会在牙齿间积累细菌，因此此空说的就是这些细菌带来的结果，故答案为A．
37．C，考查前后衔接，这一段主要讲的是引起口气的原因，因此此空C选项符合题意，说的是吸烟也是引起口气的一个重要因素．
38．E，考查前后衔接，根据下一句对刷牙给出的建议you should brush for at least 2minutes at least twice a day，可知如果刷30-45秒是不能够去除口气的，故答案为E．
39．G，考查前后衔接，空格后提到When you talk，可知此空又要提到When you breathe呼吸以及说话时喉咙的方式，故答案为G．
40．B，考查前后衔接，上一句提到you may have a medical problem，可能会有健康问题，那么就需要看医生了，故答案为B．
点评 题目要求从7个选项中选择恰当的语句填入空格处．这种类型的题目关键是符合逻辑和语境，要强调从上下文中寻找具体的解题依据．
