单选题 {{B}}Passage Six{{/B}}
We all have offensive breath at one time of another. In most cases, offensive breath emanates from bacteria in the mouth, although there are other more surprising causes.
Until a few years ago, what the most doctors could do was to counsel patients with bad breath about oral cleanliness. Now they are finding new ways to treat the usually curable condition. Bad breath can happen whenever the normal flow of saliva slows. Our mouths are full of bacteria feeding on protein in bits of food and shed tissue. The bacteria emit evil-smelling gases, the worst of which is hydrogen sulfide. Mouth bacteria thrive in airless conditions. Oxygen-rich saliva keeps their numbers down. When we sleep, for example, the saliva stream slows, and sulfide-producing bacteria gain the upper hand, producing classic "morning breath".
Alcohol, hunger, long time talking, breathing through the mouth during exercise-anything that dries the mouth produces bad breath. So can stress though it's not understood why. Some people's breath turns sour every time they go on a job interview.
Saliva flow gradually slows with age, which explains why the elderly have more bad-breath trouble than younger people do. Babies, however, who make plenty of saliva and whose mouths contain relatively few bacteria have characteristically sweet breath.
For most of us, the simple, dry-mouth variety of bad breath is easily cured. Eating or drinking starts saliva and sweeps away many of the bacteria. Breakfast often stops morning breath. Those with chronic dry mouth find that it helps to keep gum, hard candy, or a bottle of water or juice around. Brushing the teeth wipes out dry- mouth bad breath it clears away many of the offending bacteria.
Surprisingly, one thing that rarely works is mouthwash. The liquid can mask bad- breath odor with its own smell, but the effect lasts no more than an hour. Some mouth- washes claim to kill the bacteria responsible for bad breath. The trouble is, they don't necessarily reach all offending germs. Most bacteria are well protected from mouthwash under thick layers of mucus. If the mouthwash contains alcohol--as most do--it can intensify the problem by drying out the mouth.
单选题 The phrase "emanate from" in Paragraph 1 most probably means "______".
【正确答案】 C
【答案解析】第1段在陈述了offensive breath emanates from bacteria in the mouth之后又指出还有其他一些更为奇怪的诱因,可判断emanate from是在陈述offensive breath的成因。选项C“来源于”与之意思接近。emanate from来自。
单选题 Which of the following is mentioned as one of the causes of bad breath?
【正确答案】 C
【答案解析】文中第3段列举了几个引起offensive breath的原因,如hunger、alcohol等,随后又指出stress也会引起offensive breath,故选项C正确。文中只是说运动期间breathing through the mouth通过嘴巴呼吸可能引起界味,并不是说过量运动所导致的,故选项D不正确。
单选题 According to the passage, alcohol has something to do with bad breath mainly be- cause ______.
【正确答案】 D
【答案解析】文章结尾部分提到了漱口水中酒精的作用intensify the problem by drying out the mouth(使嘴巴变干,而恶化问题),可推断,酒精会影响唾液的产生,使嘴巴变干,故选项D正确。
单选题 Mouthwashes are not an effective cure for bad breath mainly because ______.
【正确答案】 B
【答案解析】结尾段落,作者给出了漱口水在对付bad breath方面的作用并不好的原因, they don't necessarily reach all offending germs, reach即是get to,故选项B正确。
单选题 We can infer from this passage that ______.
【正确答案】 A
【答案解析】从文中第5段“for most of us, the simple, dry-mouth variety of bad breath is easily cured”(对大部分人而言,简单的口干引起的口气比较容易治愈),可推断,有些offensive breath可能比较难治愈,故选项A正确。