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问题 多项选择题

有关维生素B1的性质，正确叙述的有

A．固态时不稳定
B．碱性溶液中很快分解
C．是一个酸性药物
D．可被空气氧化
E．体内易被硫胺酶破坏

答案

参考答案：B,D,E

解析： 维生素B在固态时性质稳定，水溶液的pH2.8～3.3，但不是一个酸性药物。碱性溶液中很快分解，体内则易被硫胺酶破坏，与空气接触长时间，可被氧化生成具有荧光硫色素。光和重金属离子可加速其氧化反应。

单项选择题

关于高压乙烯外送压力低的原因，下列说法不正确的是（）。

A．泵不上量

B．用户降负荷

C．过热器液面偏高

D．乙烯外送量过大
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补全对话，情景问答
从方框中选择合适的选项补全对话。
A. How about the party?
B. I stayed at home.
C. When did you go to the party?
D. Not much fun.
E. What did you do?
F. Thank you very much.
G. We sang and danced.
A: Hey, Sally! I didn't see you at the party.
B: 1.            
A: Why didn't you come?
B: I had lots of things to do.
A: 2.            
B: I cleaned my room and then I went to the library.
A: 3.            
B: Well, it wasn't too bad. I like doing some reading on weekends. 4.            
A: Great!
B: What did you do at the party?
A: 5.            
A: But after that I had to do my homework.
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