One of the characteristics of the cloud model is resource pooling. What does it mean? A) The cloud resourcs are grouped by characteristics, so they belong to the same group or pool. B) The CSP does not need to allocate fixed amounts of resources to single clients, so that resource utilization is maximized. C) Resources can be shared only by users in the same companies pool. D) The users can choose among us set or pool of resources when contracting services.