A. to observe B. observed C. observes D. observing
A. 奎尼丁 B. 氟卡尼 C. 华法林 D. 四环素
A. 5-20分钟 B. 2小时 C. 2-3小时 D. 3-4小时
A. 色氨酸 B. 苯丙氨酸 C. 赖氨酸 D. 含硫氨基酸 E. 组氨酸
A. is B. was C. has been D. had been