Assertion: The equilibrium constant is fixed and is the characteristic of any given chemical reaction at a specified temperature. Reason: The composition of the final equilibrium mixture at a particular temperature depends upon the starting amount of reactants. [AIIMS 2000] Read the assertion and reason carefully to mark the correct option out of the options given below:

• A. If both assertion and reason are true and the reason is the correct explanation of the assertion.
• B. If both assertion and reason are true but reason is not the correct explanation of the assertion.
• C. If assertion is true but reason is false.
• D. If the assertion and reason both are false.
• E. If assertion is false but reason is true.