多项选择题 Which three statements about RSTP are true?（）

单项选择题 Refer to the exhibit A frame on vlan 1 on switch s1 is sent to switch s2 when the frame is received on vlan 2,what causes this behavior?（）

多项选择题 Refer to the topology shown in the exhibit. Which ports will be STP designated ports if all the links are operating at the same bandwidth? （）