[单选题]既可顶起高处重物，又可顶起低处重物的千斤顶是()。-我要搜题网

[不定项选择题]共用题干 Face Masks May Not Protect from Super-flu

1 If a super-flu strikes,face masks may not protect you.Whether widespread use of masks will help,or
harm,during the next worldwide flu outbreak is a question that researchers are studying furiously.No results
have come from their mask research yet.However,the government says people should consider wearing them
in certain situations anyway,just in case.
2 Butit's a question the public keeps asking while the governments are making preparations for the
next flu pandemic. So the Centers for Disease Control and Prevention ( CDC ) came up with（提出）prelimi-
nary guidelines（初步指导方针）." We don ' t want people wearing them everywhere,"said the CD C. " The
overall recommendation really is to avoid exposure."
3 When that'S not possible,the guidelines say to consider wearing a simple surgical mask if you are in
one of the three following situations.First,you're healthy and can't avoid going to a' crowded place.Second,
you're sick and think you may have close contact with the healthy,such as a family member checking on
you.Third,you live with someone who'S sick and thus might be in the early stages of infection,but still need
to go out.
4 Influenza pandemic can strike when the easy-to-mutate flu virus shifts to a strain that people never
have experienced.Scientists cannot predict when the next pandemic will arrive,although concern is rising
that the Asian bird flu might trigger one if it starts spreading easily from person to person.
5 During the flu pandemic,you should protect yourself. Avoid crowds,and avoid close contact with the
sick unless you must care for someone.Why aren't masks added to this self-protection list?Because they can
help trap virus-laden（含有病毒的、充满细菌的）droplets flying through the air with a cough or sneeze.
Simple surgical masks only filter the larger droplets.Besides,the CDC is afraid masks may create a false
sense of security.Perhaps someone who should have stayed home would don an ill-fitting mask and hop on
the subway instead.
6 Nor does flu only spread through the air. Say someone covers a sneeze with his or her hand,then tou--
ches a doorknob or subway pole.If you touch that spot next and then put germy hands on your nose or
mouth,you'ye been exposed.It's harder to rub your nose while wearing a mask and so your face may get
pretty sweaty under masks.You reach under to wipe that sweat,and may transfer germs caught on the outside
of the mask straight to the nose.These are the problems face masks may create for their users.
7 Whether people should or should not use face masks still remains a question.The general public has
to wait patiently for the results of the mask research scientists are still doing. The CDC is afraid that the public may________.
A.overuse face masks
B.deal with the mask problem seriously
C.rub their faces and noses in the subway
D.protest against the mask guidelines
E.help protect people from being attacked by a flu
F.announce the results of their mask research

[单选题]既可顶起高处重物，又可顶起低处重物的千斤顶是()。A.移动式螺旋千斤顶 B. 齿条千斤顶C. 液压千斤顶D.LQ形固定式螺旋千斤顶

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[单选题]既可顶起高处重物，又可顶起低处重物的千斤顶是()。
A.移动式螺旋千斤顶
B. 齿条千斤顶
C. 液压千斤顶
D.LQ形固定式螺旋千斤顶