题目

某婴儿不能消化乳类，经检查发现他的乳糖酶分子有一个氨基酸改换而导致乳糖酶失活，发生这种现象的根本原因是( ) A．缺乏吸收某种氨基酸的能力 B．不能摄取足够的乳糖酶 C．乳糖酶基因有一个碱基替换了 D．乳糖酶基因有一个碱基缺失了 答案：C It was foolish of him to ________ his notes during that important test, and as a result, he got punished． [　　] A． stick to B． refer to C． keep to D． point to