只用于变电站进线段，有时也用于保护线路的个别薄弱环节的避雷器是( )避雷器。
A．管型
B．阀型
C．保护间隙
D．环型
参考答案：A
密度的主单位是_____，常用单位是_____，它们之间的关系是_____。
An analyst does research about various companies and stocks. A company has experienced stable earnings over the previous years and the company has a high beta. These factors best describe a:
A. cyclical company and a defensive stock.B. defensive company and a cyclical stock.C. defensive company and a defensive stock.
