The correct option is B providing shelters to thermometers
Stevenson
screen is used for providing shelter for meteorological instruments,
particularly wet and dry bulb thermometers. It is kept 1.25 meters above the
ground by legs. It is done so to avoid strong temperature gradients at ground
level. Stevenson screen has sides to encourage the free passage of air. For
reflecting heat radiation, it is painted white. It was invented by the British
engineer and meteorologist Sir Thomas Stevenson.