题目

She and her family bicycle to work, _________ helps them keep fit. A . which B . who C . as D . that 答案：A20种氨基酸平均相对分子质量为128，某蛋白质相对分子质量为10228，在形成该蛋白质分子时脱去水的总量为1548。那么组成该蛋白质的肽链数是( )A.4条 B.6条 C.8条 D.16条