卡那霉素和庆大霉素等抗生素是下列哪种菌产生的[ ]
A．细菌
B．某些放线菌
C．酵母菌
D．真菌
答案：B
基站代维服务企业的资质和基站代维服务人员的技能均分为甲、乙、丙三级。（）
In Canada, cross country skiing is a popular sport among people ______ they can enjoy excitement and adventure.
A．that
B．where
C．whom
D．which
