In a sample, which statement is TRUE about the income of the group surveyed?

Responses
A The income of the group should be lower than that of the population.The income of the group should be lower than that of the population.
B The income of the group should be proportional to that of the population.The income of the group should be proportional to that of the population.
C The income of the group should not be proportional to that of the population.The income of the group should not be proportional to that of the population.
D The income of the group should be greater than that of the population.

It is impossible to determine which statement is true without more information about the group surveyed and the population being compared to.