板蓝根抗病原微生物作用的有效成分是（）
A．苦参碱
B．癸酰乙醛
C．栀子苷
D．绿原酸
E．靛蓝
参考答案：E
--- I’m a student from Grade One. I want to become the ______ of the Music Club.
--- Welcome! But you have to sing well.
A．problem
B．sign
C．friend
D．member
按漏洞可能对系统造成的直接威胁网络安全漏洞可分为哪几类？
