题目

We work together to achieve our common purpose:_________world that is safer, cleaner and healthier than         one we found. A. the;the               B. a;不填               C. a;the                    D. the;不填 答案:C某二十二肽被水解成1个四肽,2个三肽,2个六肽,则这些短肽的氨基总数的最小值及肽键总数依次是( )A.6,18 B.5,18 C.5,17 D.6,17
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