The correct option is C Assertion is correct but Reason is incorrect
Each mitochondria is a double membrane-bound structure with the outer
membrane and the inner membrane dividing its lumen distinctly into two
aqueous compartments, i.e., the outer compartment and the inner
compartment. The inner compartment contains the matrix. The outer
membrane forms the continuous limiting boundary of the organelle. The
inner membrane forms a number of infoldings called the cristae (sing.
crista) towards the matrix. The cristae increase the surface area. So,
the correct answer is 'Assertion is correct but Reason is incorrect'.