To solve this question, the user needs to have knowledge about the RD parameter in telecommunication. The RD (Radio Network Dimensioning) parameter is used to define the size of the radio network. It is used to control the number of cells in a radio network and the distribution of those cells.
Now, let's go through each option and explain which one is not a valid value for the RD parameter:
A. R: This is a valid value for the RD parameter. It stands for Rural.
B. RNC: This is a valid value for the RD parameter. It stands for Radio Network Controller.
C. NR: This is a valid value for the RD parameter. It stands for New Radio.
D. RC: This is not a valid value for the RD parameter. It is not an abbreviation for any radio network dimensioning term.
E. None: This is not a valid value for the RD parameter as it does not define any radio network dimensioning parameter.
Therefore, the answer is: D. RC.