If a Political Survey Is Conducted at a Women's Gym

Multiple Choice

If a political survey is conducted at a women's gym, which of the following would be most likely to cast doubt on the external validity of these studies?

A) The surveyors were not members of the gym.
B) The surveyors were members of the gym.
C) All of the participants were women.
D) All of the participants were gym members.
E) All of the participants had just exercised or were about to exercise.