香港房地产经纪业的基本制度主要有以下一些制度( )。

A．执业资质制度

B．教育训练制度

C．佣金自由竞争制度

D．纠纷处理制度

E．信誉及风险赔偿制度

—What time will Mr Brown be back to China?

—Sorry. I don’t know ______.

A．when did he go abroad

B．why he is going abroad

C．how soon will he be back

D．how long he is going to be there