The correct option is A Mean
The mean is the most frequently used measure of central tendency because it takes into account all the observations, and lies between the extremes.
However, extreme values in the data affect the mean.
For example: If one class has frequency, say 2, and the five others have frequency 20, 25, 20, 21, 18, then the mean will certainly not reflect the way the data behaves.
So, in such cases, the mean is not a good representative of the data.