in the study lost in thought for a long time, I suddenly realized that nothing in the world remains     .

A．Having sit; unchanged

B．To sit; unchanging

C．Sitting; unchanged

D．Sitting; unchanging

一国对出口市场提供的服务收费比在国内市场上低，称为（）。

A、服务倾销

B、运费倾销

C、间接倾销

D、产品倾销