Gas pressure in a closed system is caused by resultant force of all combines collisions. The correct option among all the options that are given in the question is the third option or option "C". The other options can easily be ignored. I hope the answer comes to your help.
In a closed system, when matter present in the system is hot then there will be number of collisions between the molecules of matter. As a result, molecules will have kinetic energy.
This energy will be given off by the molecules in the form of heat due to constant collisions.
Therefore, we can conclude that gas pressure in a closed system is caused by heat given off by constant collisions.
