Homeowners Were Asked to Display a Small "Be a Safe

Homeowners were asked to display a small "Be a Safe Driver" sign in their windows. Later, they were asked to install a large, ugly "Drive Carefully" sign on their front lawns. How likely would they be to agree, compared to people who had never been asked to display the small sign?

A) No one would agree to put up an ugly sign.
B) People who put up a small sign would be more likely to put up the ugly sign than people who were not asked to display the small sign.
C) People who already displayed the small sign would feel they had done their part and would be less likely to agree.
D) Social norms would make it nearly impossible for anyone in either group to refuse.