The correct answer is a. There is an increase in the number of collisions between particles and the walls of the container.
Explanation:
Gas molecules in a container collide with each other and with the wall of the container. Whenever a molecule of gas collides with the wall of the container it exerts certain force on the wall and pressure is the sum of all the forces applied on the wall of container by gas particles.
So if more gas is added in the container then more gas particles will exert force on the wall of the container and more number of collisions will occur which will increase the pressure inside the container.
Therefore the correct answer is a. There is an increase in the number of collisions between particles and the walls of the container.
