A. The words were so hard. B. The words took up so much space. C. It took so long to read a book. D. It was difficult to read. 参考答案:C 答案解析:解析:由第五段最后一句And reading it took a very long time可知。
第23题: [单项选择]
盐酸吗啡中的罂粟酸 A. 配制成50mg/ml的溶液,测定旋光度,不得过-0.4° B. 配制成2.0mg/ml的溶液,在310nm处测定,吸收度不得大于0.05 C. 供试品溶液加稀盐酸5ml与三氯化铁试液2滴,不得显红色 D. 供试品溶液加硝酸与水混合液,除黄色外不得显红色或淡红棕色 E. 薄层色谱法 参考答案:C