Hmm, now I see the option to mark as a solution. I don't know why it was missing. I reopened my thread's page couple of times and it wasn't showing up. Now it does.This happens when one fails to pay attention and sets up the wrong type of thread. "Discussion" is the default type and does not have a best answer option. Set the type to "Question" if you want the best answer option available. If you have a specific thread that needs to be changed then name it here and one of the moderator team can change it.