A isn’t useful to scope the process, get a basic understanding of the flow, and indicate the main steps, but it is relevant for discussing details of process improvements or even software driven support of the process.
B is simple because it assumes that a solution is always found to be explained to the customer. The model lacks all details of collaboration between the involved employees, that is important to the ITIL´s Incident Management process.
C shows the 2nd level support agent should figure out if the customer can fix the problem on her own, but if the agent is not sure about this he must deliver the responsability to a 3rd level agent or return to the 1st level, as recommended by ITIL.
D depicts the ITIL´s Release and Deployment Management process in which the account manager should try to handle that request on his own and explain the solution to the customer, then hand over the issue to a 2nd level support agent, who will hand over to upper level support, in a chain.
E shows the ITIL´s Service Portfolio Management process of a software manufacturer that is triggered by a customer requesting help from the account manager because of a well defined problem.