在SDH网管中，DCC falure告警级别为（）。
A、紧急告警
B、主要告警
C、次要告警
D、提示告警
参考答案：A
If Newton lived today,he would be surprised by what_____in science and technology.
A．had discovered
B．had been discovered
C．has discovered
D．has been discovered
简述产品组合策略的选择？
