—Did you have any difficulty catching yesterday's lecture?

—No. The professor spoke very clearly to make his speech easy _____.[ ]

A. understood                  

B. understand   

C. understanding              

D. to understand

农业银行服务“三农”和县域经济发展的总体要求包括（）。

A．成本可控

B．收益倍增

C．风险可控

D．商业可持续