---- Is there anything about your high school life you wish you’d done differently?

---- I regret that I ______ earlier what I really like doing.

A．don’t realize

B．didn’t realize

C．haven’t realized

D．hadn’t realized

邮件运输具有（）、依附性、时效性、复杂性等特点。

A、超区域性

B、统一性

C、独立性

D、基础性