市场经济是()。
A．一种基本经济制度
B．一种经济运行方式
C．一种资本组织形式
D．一种生产经营方式
参考答案：B
— Has James finished his report on his Enquiry Learning yet?
— I'm not sure. She _____ on it last week. [ ]
A. was working
B. has worked
C. worked
D. had worked
Na+离子通过离子通道的跨膜转运过程属于（）
A．单纯扩散
B．易化扩散
C．主动转运
D．出胞作用
E．人胞作用
