Which is an example of a bidirectional relationship between porn and violence?

Which is an example of a bidirectional relationship between porn and violence?
 
  a. From a sociobiological perspective, aggressive men have an increased drive to procreate and thus pornography is a natural extension of their aggression.
  b. In general, men are more aggressive than women, thus creating the false association that pornography increases the violent behavior of men toward women.
  c. Men who have higher than average testosterone levels are both more sexually aggressive and have a hypersexed drive.
  d. Men who are prone to sexual violence are more drawn to sexually violent porn, and thus are more likely influenced by that porn.