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【多选题】
实验前的准备事项有哪些?( )A.
熟悉实验室及其周围环境,如:水门、各条电路控制电闸的位置及各电闸的作用,以便发生意外时关闭；
B.
了解仪器的性能和注意事项、化学试剂的性质及安全说明、和本实验中的安全注意事项；
C.
检查仪器是否完整无损,装置是否正确妥当；实验进行时应该经常注意仪器是否有无漏气、破裂、反应进行是否正常等情况；
D.
不需要准备。
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知识点：
皮皮学刷刷变学霸
举一反三
【单选题】If a person shows no fear in face of danger, he or she is _______.
A.
gentle
B.
self-centered
C.
patient
D.
courageous
【简答题】shore up _____________________
【简答题】If a person shows no fear in face of er, he or she is .
【单选题】The crucial factor was the ( ) of several days during which steps were taken to shore up the weakened wall.
A.
delay
B.
beginning
C.
work
D.
last
【单选题】"These are the times that try men' s souls", these words were once read to George Washington' s troops and did much to shore up the spirits of the revolutionary soldiers. Who is the author of these w...
A.
Benjamin Franklin
B.
Thomas Jefferson
C.
Thomas Paine
D.
George Washington
【简答题】If a person shows no fear in face of er, he is ______ 有勇气的
【简答题】If a person shows no fear in face of er, he or is _________
【判断题】The crucial factor was the delay of several days during which no steps were taken to shore up the weakened wall.
A.
正确
B.
错误
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