Which command do you enter to troubleshoot a misconfigured Ether Channel?

Which command do you enter to troubleshoot a misconfigured Ether Channel?
A . CORE-SW (config-if) #spanning-tree guard root
B . CORE-SW (config-if) #spanning-tree loopguard default
C . CORE-SW (config-if) #spanning-tree etherchannel guard msconfig
D . CORE-SW (config) #spanning-tree etherchannel guard msconfig

Answer: D

Explanation: