苯二氮革类结合位点在脑内分布密度高的部位是：
A．脊髓
B．中脑
C．边缘系统
D．大脑皮质
E．脑干
参考答案：D
实验组和对照组必须均衡，唯一不同的是（）
A.观察指标
B.观察时间
C.实验因素
D.抽样误差
E.系统误差
In software engineering and systems engineering, （）is a description of a system’s behavior as it responds to a request that originates from outside of that system.
A.black box
B.business rule
C.use case
D.traceability matrix
