题目

下列各项与蛋白质结构多样性无关的是（     ） A．氨基酸至少含一个氨基和一个羟基   B．构成蛋白质的多肽链的数目 C．构成蛋白质的多肽链的空间结构     D．氨基酸的数目、种类和排列顺序 答案：A —Your colleague is speaking English with fluency. —It's no wonder．She ____ in the UK for a year as a visiting professor A. worked    B. has worked C. had worked   D. has been working