In a Study for Which the Sample Does Not Represent

In a study for which the sample does not represent the population for the question of interest

A) the results cannot be extended to the population and a cause and effect conclusion cannot be made.
B) the results cannot be extended to the population, but a cause and effect conclusion can be made if the treatments were randomly assigned.
C) the results can be extended to the population if they are statistically significant.
D) the results can be extended to the population if the sample size is large enough.