Which agent will be selected when the Resource Selection Criteria is set to circular routing?（）

A、A.the agent who has been in the Available state for the longest amount of time  

B、B.the next available agent with the highest priority, as determined by the agent order in the Resources list

C、C.the next available agent, based on the last agent selected and the agent order in the Resources list  

D、D.the agent assigned to the selected Resource Group and is thus qualified to be selected