第13题: [单项选择]Only when they are injured______. A. will some animals attack a human being B. a human being will be attacked by some animals C. some animals will attack a human being D. that some animals attack a human being 参考答案:A 答案解析:[解析] 考查倒装句。含有only的状语用在句首时,句子要倒装。
第14题: [单项选择]嘧啶环中两个氮原子来自()。 A. Gln+NH3 B. Gln+Asp C. Gln+Glu D. NH3+Asp E. Gln中的两个N原子 参考答案:D