A Couple Refuses to Mow Their Lawn

A couple refuses to mow their lawn. Their neighbors take them to court, using economic logic to argue that

A) property rights are poorly defined because externalities exist
B) they are free riders and entitled to the value of the externalities
C) although there are no third parties because property rights are clear, the market still generates market failure
D) although property rights are clear, there are still externalities that should be considered
E) market failure can be avoided if the couple sells their property to any of the neighbors