Kingdom Fungi. Mostly are single celled bacteria, they emit sunlight by means of photosynthesis that allows them to make food for themselves and also they have another food serve except for the sunlight and eats some single cell organism and that would call them as heterotrophic
Because bacteria can be good for the environment
The armpit isn't the most precise but it is close. Under the tongue, across the forehead, as long as you have the proper tools (thermometer, the thermometer meant for foreheads) you should get a fairly accurate reading.