Brownian motion is the random motion of particles due to molecular bombardment. In which states of matter is Brownian motion observed?
A gases, liquids and solids
B gases and liquids only
C gases and solids only
D liquids and solids only

The illuminance of a surface varies inversely with the square of its distance from the light source. if the illuminance of a surface is 120 lumens per square meter when its distance from a certain light source is 6 meters, by how many meters should the distance of the surface from the source be increased to reduce its illuminance to 30 lumens per square meter?