A.) Adding more of gas C to the system
A.) is correct because the reaction wants to keep the same amount of reactants and products that sustain equilibrium. If you are increasing the amount of gas C, this will push the reaction to make more of the reactants to restore the balance.
B.) is incorrect because heat is a form of energy. As previously stated, when you add more material to the reactants side, the equilibrium shifts to the product side to restore equilibrium.
C.) is incorrect because when the volume is increased, the equilibrium will shift to the side with the greater amount of moles of gas. There is 1 mole of gas on the reactant side (from A (g)) and 3 moles of gas on the products side (from 3 C (g)). Therefore, the reaction will shift to the product side.
D.) is incorrect because if the material on the product side is decreasing, the equilibrium will want to make up that difference by shifting to the product side.
reactants ---> products
vanderwaal's forces of attraction are the electrostatic intermolecular forces that exist in a molecule due to the temporary or permanent dipoles that are developed in a molecule. in , the major intermolecular forces are dipole-dipole interactions as the molecule is polar (bent structure). so the vanderwaal's forces of interaction in between molecules are the permanent dipole-dipole interactions that develop due to the dipole that exists in between the polar h - s bond. the positively charged hydrogen atom is attracted towards the negative end of the dipole that is sulfur of the adjacent molecule. therefore, these forces of attraction are relatively stronger than that of london dispersion forces that exist in non polar molecules.