Forces of attraction between the particles will be weak when they are far apart from each other. Hence, only then the molecules will be able to move rapidly and they can be ignored at ordinary conditions.
For example, in gases molecules are held together by weak Vander waal forces.
Whereas solids and liquids have more force of attraction between their molecules as compared to gases as they cannot be ignored under ordinary conditions.
Thus, we can conclude that in substance C forces of attraction among the particles so weak that they can be ignored under ordinary conditions.
Substance C can be compared with gaseous particles in which intermolecular forces are so weak because particles are far from each other. Hence option C is correct.
