问题
单项选择题
气相色谱填充柱的理论塔板数可以达到2000块/米，对于高效液相色谱，每米的理论塔板数可以达到（）块。
A、4000
B、10000
C、20000
D、30000
答案
参考答案：D
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气相色谱填充柱的理论塔板数可以达到2000块/米，对于高效液相色谱，每米的理论塔板数可以达到（）块。
A、4000
B、10000
C、20000
D、30000
参考答案：D
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| Tim was a 1 boy. He was not a very good student, and he did not like _2_ homework 3 he enjoyed doing other things in his free time. Usually, he did not do his homework and when he did it he always _4 a lot of mistakes. One day his math teacher 5 Tim's homework and saw that he got all his 6 right. He was very _7_ and rather (相当) _8_. He called Tim to his desk and said to 9 . "You got all your homework 10_ this time, Tim. _11_? Did your father help _12_?" Usually Tim's father helped him 13 his homework, but the evening before this, he had not been able to (能), because he _14_ at home that evening, so Tim answered, "No, sir, he was very busy last night, 15 I had to do it all by myself." | ||||
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