Le Chatelier's principle: when a system is subjected to a stress, it will shift in a way to counteract the stress.
There a 4 types of changes that can occur:
Concentration Change: Altering the concentration of reactants or products, or changing the pressure (for reactions involving gases), can cause the system to shift to restore equilibrium. An increase in concentration of reactants causes a shift to products while a decrease causes a shift to reactants. For increase in products it shifts to reactants and for a decrease in product concentration it will shift towards the products. Essentially, shift away from addition and shift towards removal.
Temperature Change: Changing the temperature affects the equilibrium position differently depending on whether the reaction is exothermic or endothermic. Increasing the temperature of an endothermic reaction will make equilibrium shift to the reactants, if it is increased it will shift to the products. For an exothermic reaction, if temperature is increased, equilibrium will shift to the reactants and if temperature is decreased it will shift to the products.
Volume/Pressure Change: For reactions involving gases, altering the volume of the container or changing the pressure can impact the equilibrium position. Decreasing the volume/increasing the pressure favors the side with fewer moles of gas, while increasing the volume/decreasing the pressure favors the side with more moles of gas.
Addition/Removal of a Catalyst: The addition or removal of a catalyst does not change the equilibrium position but speeds up the attainment of equilibrium by increasing the reaction rate in both the forward and reverse directions.
According to this principle, an increase in temperature for an endothermic reaction will cause the equilibrium to shift towards he products. Therefore, b is correct.
