–Why isn’t your brother good at math?

-- Because he thinks math is __________ than any other subject.

A．difficult

B．much difficult

C．more difficult

D．the most difficult

TCP/IP协议是一种开放的协议标准，下列哪些是它的特点（）

A、独立于特定计算机硬件和操作系统

B、统一编址方案

C、政府标准

D、标准化的高层协议