—What did Frankie do when he was young?

—He______ play the piano very often.[ ]

A. uses to        

B. used to        

C. is used to        

D. was used to

关于应用系统统一开发平台的建设思路，下面哪几项是正确的（）

A、统一管控

B、统一设计、研发

C、统一发布、统一技术服务

D、以上说法都不对