Why does my Yahoo answers page ask me to choose best answer ?

Question

after only just a few people answer even though Its an open question and Iv extended the time..... I see some people have 30 answers and I seem to get 6 or 7 and then am asked for best answer?

Answer 1

idk just pick anyone and then for comment say all were good and thanks

Answer 2

It seems odd that this happens sometimes but not always - where is the logic?  I'm not sure there is any.