第8题: [单项选择]自然界中的氨基酸常见分类原则是( )。 A. 按蛋白质来源分类 B. 按营养价值分类 C. 按化学结构分类 D. 按营养价值和化学结构分类 参考答案:D 答案解析:[解析] 氨基酸分类 [解析] 氨基酸按化学结构式分为脂肪族氨基酸、芳香族氨基酸和杂环氨基酸。在营养学上根据氨基酸的必需性分为必需氨基酸、非必需氨基酸和条件必需氨基酸。
A. he was very much interested in the sport B. he intended to revenge on the bike thief C. he found a policeman as his best trainer D. he had got boxing lessons from the police 参考答案:B 答案解析:[听力原文]17-20 At first Muhammad Ali-Cassius Clay had no intention of boxing. After his bike was
第10题: [单项选择]There is little doubt that the arts in America will be greatly ______ by the large numbers of European artists who are taking up residence and often citizenship in the United States. A. erupted B. enriched C. erased D. elicited 参考答案:B 答案解析:[句意] 毫无疑问，美国的艺术会因居住在美国和取得美国公民权的数量很多的欧洲艺术家而得到极大丰富。
[辨析] 动词辨义。erupt意为“爆发，喷发”，如：The volcano erupted af
