The correct answer to your question is:
(c) Network intelligence
In the context of Cognitive Radio (CR) and Radio Environment Maps (REM), combining learning with data mining helps enhance network intelligence. This is because cognitive radios utilize data from the radio environment to make decisions on spectrum management, interference avoidance, and dynamic adaptation. By applying learning algorithms and data mining techniques, cognitive networks can improve their performance by predicting and adapting to the radio environment based on past experiences, thus achieving more efficient spectrum usage and network optimization.