What was the major change in agriculture during the 19th century

A．Crop production became increasingly specialized.

B．Economic depressions lowered the prices of farm produce.

C．New banking laws made it easy to buy farmland.

D．The United States increased its agricultural imports.

下列属于球场营运的硬件设施要素的是（）。

A.球场服务程序

B.球场信息系统

C.球场给排水系统

D.球会作业流程