什么是农业生产函数？建立和应用农业生产函数模型应该注意那些问题？

A. 请购单
B. 订单
C. 定单
D. 验收单

A. It‘ll be ready in the afternoon, sir.
B. I‘d like you to help me.
C. I know nothing about the report.
D. Leave it to tomorrow.

A. 20~40A
B. 50~80kA
C. 20~40kA
D. 50~80A