The Brownian motion increases on account of.

The Brownian motion increases on account of.
1) Decreasing the size of the particle.
2) Decreasing the density of medium.
3) Decreasing the temperature.

a) 1, 2 only
b) 2, 3 only
c) 1, 2, 3 only
d) 1, 3 only

Answer: (A)