电子商务系统安全管理包含两个方面的内容：一是计算机网络安全管理，二是电子商务（）安全管理
参考答案：交易
—You look so worried, what’s wrong?
—More and more people like me become to worry about the __________ pollution after the haze (雾霾) appeared in Beijing and some other cities in China.
A．water
B．air
C．noise
D．Soil
A．5A
B．5A
C．3.5A
D．3.5A
