TEXT B We all have offensive
breath at one time or another. In most cases offensive breath emanates
from bacteria in the mouth, although there are other, more surprising
causes. Until a few years ago, 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 (唾液) slows. Our mouths are full of
bacteria feeding on protein in bits of food and shed tissue. The bacteria emit
smelling gases, the worst of which is hydrogen sulfide (硫化物).
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 gains the upper hand, producing classic "morning
breath". Alcohol, hunger, too much 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, file 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 had breath because 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 mouthwashes 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 (黏液). If the mouthwash contains alcohol—as most do—it can
intensify the problem by drying out the mouth. We can infer from this passage that _______.
A．offensive breath can’t easily be cured B．elderly people are less offended by bad breath C．heavy drinkers are less affected by bad breath D．offensive breath is less affected by alcohol