— Mum, it is nice weather.I want to skate this afternoon.

— Don't you think the ice on the lake is too thin to__________your weight?[      ]

A. carry        

B. bear

C. catch  

D. take

专家系统的核心部分是( )

A．知识库子系统

B．知识获取子系统

C．咨询解释子系统

D．推理子系统