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问题 单项选择题

OSPF路由协议区域间的环路避免是通过哪种方式实现的？（）。

A.分层结构的拓扑实现

B.基于SPF计算出的无环路径

C.基于areaID

D.基于ASID

答案

参考答案：A

阅读理解
Laboratory work is your chance to learn science first-hand. It can be fun but you must be careful to prevent injury. Listen closely when your teacher reads and explains the rules before your first lab lesson.
LABORATORY RULES
Throughout the lesson
Do not enter the science lab without the teacher’s permission.
No food or drinks are to be allowed in the science lab.
Before the Experiment
Read all instructions carefully before every experiment.
Prepare all apparatus (仪器) and arrange them so that you will not knock them over while doing the experiment.
During the Experiment
If you are unsure of how to use any apparatus or how to operate, ask your teacher for help.
Never smell or taste chemicals unless your teacher gives permission.
After the Experiment
Wash all apparatus after use and return them to the places where they were.
Throw waste materials in proper waste baskets.
First Aid
Report all accidents to your teacher immediately.
If you spill (溅出) any chemicals onto your body of clothing, wash with plenty of water and report to your teacher.
小题1:Your teacher will probably tell you the rules above        the first lab lesson.
A．beforeB．sinceC．duringD．after
小题2:Before every experiment, you should       .
A．taste the chemicals first
B．clean all the apparatus
C．read all instructions carefully
D．report all the accidents to the teacher
小题3:When you are not sure how to use all apparatus,       .
A．try them on your ownB．put them back
C．ask your teacher for helpD．read the rules carefully
小题4:It is clear that you can       .
A．bring food into the lab
B．enter the lab anytime
C．smell chemicals as you like
D．learn science directly in the lab
小题5:If you get chemicals on the clothing, you can find ways to solve it in the part       .
A．Before the ExperimentB．First Aid
C．During the ExperimentD．After the Experiment
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单项选择题

5岁女孩，自幼身体瘦弱，易患感冒。查体：心前区稍隆起，未触及震颤，胸骨左缘第2肋间可闻及Ⅱ级收缩期杂音，第二心音亢进，固定分裂。最可能出现的超声心动图改变的是（）

A.左室内膜增厚

B.左室流出道增宽

C.左房增大，主动脉增宽

D.右房增大，肺动脉道增宽

E.肺动脉增宽
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