血药浓度下降一半所需的时间为（）。
A．潜伏期
B．持续期
C．失效期
D．残留期
E．消除半衰期
参考答案：E
解析：
[知识点] 药物的量效关系
The audience, ________ , enjoyed the performance.
A．most of them were students
B．most of whom were students
C．whom they were students
D．they were mostly students
一年级学生观察的精确性水平很低，不能全面细致地感知客体的细节。
