下列（）属于二次设备。
A.断路器
B.电源互感器
C.远动装置
D.变压器
参考答案：C
that we can't get the necessary equipment , we will have to give up the experiment. [ ]
A. If
B. Supposed
C. Provide
D. Assuming
简述链球菌的主要致病物质。
