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问题 判断题

裂解汽油加氢装置停车检修，当需要对反应器进行维修时，如果催化剂在停车前不久已再生过，也可不安排催化剂再生。

答案

参考答案：错

解析：裂解汽油加氢装置停车检修为防止串入空气聚合物自燃，催化剂必须安排再生。

问答题

Traditional medicine is the sum total of knowledge, skills and practices based on the theories, beliefs and experiences indigenous to different cultures that are used to maintain health, as well as to prevent, diagnose or treat physical and mental illnesses. Traditional medicine that has been adopted by other populations (outside its indigenous culture) is often termed alternative or complementary medicine. Herbal medicines include herbs, herbal preparations, and finished herbal products that contain parts of plants as active ingredients. In some Asian and African countries, 80% of the population depend on traditional medicine for primary health care. In many developed countries, 70% to 80% of the population has used some form of alternative or complementary medicine, such as acupuncture.
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单项选择题

下列题的关系代数操作基于如下的关系R和S：

R
A B C
a1 b1 5
a1 b2 6
a2 b3 8
a2 b4 12
S
B E
b1 3
b2 7
b3 10
b4 2
b5 2

若关系R和S的关系代数的操作结果如下，这是执行了( )。

A R.B C S.B E
a1 b1 5 b2 7
a1 b1 5 b3 10
a1 b2 6 b2 7
a1 b2 6 b3 10
a1 b3 8 b3 10
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