单项选择题 In a high-availability network, which command, when placed on ports that have connected end stations, will allow you to prevent delays in service for end stations by placing a port in blocking mode?（）

多项选择题 In a RSTP implementation, which of the following two link types are used? （）(Choose two.)

单项选择题 As an experienced network engineer, you are asked to troubleshoot a CIS network outage. During the troubleshooting process, you notice that one of your colleagues connects additional devices to the network with the use of his own switch. With the purpose of improving speed, the switch is attached to both network ports in an office, which leads to bridge loop. Enabling which of the following feature will be able to prevent this problem from happening again?（）