When you've asked a question and a post has answered it to your satisfaction you can set that post as the "Best Answer". This article will show you how to set or remove a post as the Best Answer and where you can do it:
If you have set a Best Answer in error or decide that another post better answered your question then you can remove your original choice.
To remove a post as the Best Answer:
Click Options on the top right hand side of the post you set as Best Answer and select the "Not the Best Answer" option (6th in the list of options).
Please note that if your using a Mobile device you will need to be viewing your post on FULL view mode on your device to make the above selection. The options menu is not available within the Mobile View.