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问题 选择题

国际上曾把原定在2000年全球禁用氟利昂（冰箱制冷剂）的时间提前到1996年，主要是为了保护大气平流层中的一种物质不受破坏，这种物质的同素异形体是

A．O2

B．H2

C．N2

D．O3

答案

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

M型超声心动图二尖瓣前叶运动曲线上A峰对应哪个心脏运动时相（）

A.等容舒张期

B.快速舒张期

C.心房收缩期

D.缓慢舒张期

E.心室收缩期
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