将Teachers表的查询权限授予用户U1和U2，并允许该用户将此权限授予其他用户。实现此功能的SQL语句如下（ ）。
SQL中使用grant和revoke语句向用户授予或收回对数据的操作权限。
grant语句向用户授予权限，revoke语句收回已经授予用户的权限。
grant语句的一般格式为：
grant<权限>[，<权限>]…on<对象类型><对象名>[，<对象类型><对象名>]…to<用户>[，<用户>]…[with grant option]，故可以排除B项、D项。
with grant option的意思是：权限赋予/取消是级联的，如将with grant option用于对象授权时，被授予的用户也可把此对象权限授予其他用户或角色，但管理员收回用with grant option授权的用户对象权限时，权限会因传播而失效。而WITH PUBLIC是可将权限赋给所有的用户，故应选择C项。
The Internet of（ 1）（IoT） describes physical objects that are embedded with Sensor，processing abilities，softwares，and other technologies that connect with other devices and systems over the （ 2） or other communication and exchange data networks .Over the past few years, IoT has become one of the most important technologies of the （ 3 ） centuryWe can connect objects to the Internet via embedded devices. By means of（ 4） computing, the cloud, big data, and mobile technologies, physical things can share and collect data with minimal human intervention. Traditional fields of embedded systems，wireless （ 5） networks （WSNs），control systems，automation, independently and collectively enable IoT.回答5处
The Internet of（ 1）（IoT） describes physical objects that are embedded with Sensor，processing abilities，softwares，and other technologies that connect with other devices and systems over the （ 2） or other communication and exchange data networks .Over the past few years, IoT has become one of the most important technologies of the （ 3 ） centuryWe can connect objects to the Internet via embedded devices. By means of（ 4） computing, the cloud, big data, and mobile technologies, physical things can share and collect data with minimal human intervention. Traditional fields of embedded systems，wireless （ 5） networks （WSNs），control systems，automation, independently and collectively enable IoT.回答4处
The Internet of（ 1）（IoT） describes physical objects that are embedded with Sensor，processing abilities，softwares，and other technologies that connect with other devices and systems over the （ 2） or other communication and exchange data networks .Over the past few years, IoT has become one of the most important technologies of the （ 3 ） centuryWe can connect objects to the Internet via embedded devices. By means of（ 4） computing, the cloud, big data, and mobile technologies, physical things can share and collect data with minimal human intervention. Traditional fields of embedded systems，wireless （ 5） networks （WSNs），control systems，automation, independently and collectively enable IoT.回答3处
The Internet of（ 1）（IoT） describes physical objects that are embedded with Sensor，processing abilities，softwares，and other technologies that connect with other devices and systems over the （ 2） or other communication and exchange data networks .Over the past few years, IoT has become one of the most important technologies of the （ 3 ） centuryWe can connect objects to the Internet via embedded devices. By means of（ 4） computing, the cloud, big data, and mobile technologies, physical things can share and collect data with minimal human intervention. Traditional fields of embedded systems，wireless （ 5） networks （WSNs），control systems，automation, independently and collectively enable IoT.回答2处
The Internet of（ 1）（IoT） describes physical objects that are embedded with Sensor，processing abilities，softwares，and other technologies that connect with other devices and systems over the （ 2） or other communication and exchange data networks .Over the past few years, IoT has become one of the most important technologies of the （ 3 ） centuryWe can connect objects to the Internet via embedded devices. By means of（ 4） computing, the cloud, big data, and mobile technologies, physical things can share and collect data with minimal human intervention. Traditional fields of embedded systems，wireless （ 5） networks （WSNs），control systems，automation, independently and collectively enable IoT.回答1处
管理员要检查本地主机TCP/IP协议是否能够正常工作，应使用下面（ ）命令。
在Windows系统中，可以在“运行”对话框中使用（ ）打开命令行窗口。
在Windows 系统中，要持续ping某主机，应使用（ ）选项。
在Linux系统中，管理员在DHCP服务器的配置文件中添加了下面一段代码:subnet 192.168.20.0 netmask 255.255.255.0{range 192 .168 .20 .10 192 .168 .20.50;option domain-name-server ns1 .internal.example.comoption routers 192 .168 .20.254;option broadcast-address 192.168.20.255;default-lease-time 1200;max-lease-time 360000;}当该DHCP服务器启动后，下面分配给客户端的IP地址中，正确的是（ ）.
在Linux系统中，通常使用（ ）为用户提供FTP服务，其配置信息存放在（回答此处）目录中。
