色氨酸通过脱氨和氧化脱羧作用，可转变成______从尿中排出；色氨酸还可转变成______，它是组成辅酶Ⅰ和辅酶Ⅱ的
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根据我国现行证券交易佣金收取标准的规定，A股每笔交易佣金最低收取()。
A. O元
B. 1元
C. 5元
D. 100元
嘧啶环的第1位氮及第4、5、6位碳来自______，第2位碳和第3位氮来自______。
Which statement is true of the methane emissions of plants in the experiment？
A. The lower the temperature,the higher the amount of methane emissions
B. Living plants release less methane than dried plants at the same temperature
C. When exposed to sunlight, plants stop releasing methane
D. The higher the temperature,the greater the amount of methane emissions
52
A. simpler
B. more complex
C. more meaningless
D. more troublesome
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