问题：

[多选] Which two statements concerning STP state changes are true？ （）

A . Upon bootup，a port transitions from blocking to forwarding because it assumes itself as root.
B . Upon bootup，a port transitions from blocking to listening because it assumes itself as root.
C . Upon bootup，a port transitions from listening to forwarding because it assumes itself as root.
D . If a forwarding port receives no BPDUs by the max_age time limit， it will transition to listening.
E . If a forwarding port receives an inferior BPDU， it will transition to listening.
F . If a blocked port receives no BPDUs by the max_age time limit， it will transition to listening.