6: The relationship between how many violent TV programs children watch in their homes, and high levels
  of aggression, is an example of:

   A: a causal relationship

    Incorrect.
To establish a causal relationship, we must manipulate one variable (an independent variable) and see changes in another variable (a dependent variable).  In Choice A, what we are doing is measuring the amount of TV children watch and correlating this information with children's level of aggression.  All this information can tell is that the two are positively related, but this relation could be caused by other factors, such as the parents' level of aggression.  The relationship could also work the other way, such that more violent children prefer violent TV shows.