吸烟是目前危害人类健康最严重的不良行为之一，因为吸烟是多种疾病的独立致病因素，这是因为从烟草中分离出的化学物质有（）多种，其中有害物质有30多种，具统计，全球每年死于与吸烟相关的疾病人数达300万人。
A. 1200
B. 1250
C. 1300
D. 1350
What is IPv6 router solicitation?（）
A. a request made by a node to join a specified multicast group
B. a request made by a node for its IP address
C. a request made by a node for the IP address of the DHCP server
D. a request made by a node for the IP address of the local router
微信支付 
支付宝支付