Question

why the doctor keeps the thermometer under the r
tongue ?

Answer 1

because this is the place where they can measure correct body temperature

Answer 2

doctor always keeps the thermometer under the tongue to get the exact temperature of the bod as there is no such materials which can make a difference in the temperature,for example we have hairs in our underarms which absorb temperature and increase the readings of the thermometer by 2 to 3 degrees.