Answer:
a. standard deviation
Step-by-step explanation:
Dispersion is a measure of variability in a given data i.e the level or extent of spread of a data. This can easily be measured for a random variable by considering its standard deviation.
The standard deviation would show the extent to which each value is different from the mean. Thus showing the extent of the dispersion of variables.
Therefore, to measure the dispersion of a random variable, look at its standard deviation.