Subject: mathqa
Question: a dog breeder currently has 9 breeding dogs . 6 of the dogs have exactly 1 littermate , and 3 of the dogs have exactly 2 littermates . if 2 dogs are selected at random , what is the probability e that both selected dogs are not littermates ?
Option: 
A: 2 / 9
B: 7 / 9
C: 5 / 6
D: 1 / 6
Answer: C