题目

Franz Kafka wrote that “a book must be the ax(斧子) for the frozen sea inside us. ” I once shared this sentence with a class of seventh graders, and it didn’t seem to require any explanation. We’d just finished John Steinbeck’s novel Of Mice and Men. When we read the end together out loud in class, my toughest boy, a star basketball player, wept a little, and so did I. “Are you crying?” one girl asked, as she got out of her chair to take a closer look. “I am,” I told her, “and the funny thing is I’ve read it many times.” But they understood. When George shoot下列实验中需要使用光学显微镜才能清晰观察到实验现象的是（    ） A．叶绿体中色素的提取和分离    B．检测生物组织中的糖类 C．探究pH对酶活性的影响          D．检测生物组织中的油脂