-judging your friend
all the other actions can be helpful, judging them will just push them away to the point that they will not listent to you or even be your friend anymore.
The brown stuff is called plaque. This forms on your teeth when you eat and its something you can't get rid of. There is tooth paste that can help maintain it.
Red blood cell antibodies may show up in your blood if you are exposed to red blood cells other than your own. Antibody serology tests check for the presence or level of specific antibodies in the blood.
