Option (A): Cell division indeed replaces lost cells in certain tissues, making this statement correct.
Option (B): Growth in living organisms happens internally and externally; it is not just from outside. This is incorrect.
Option (C): Metabolism is correctly described as the sum total of all chemical reactions occurring in the living organism, which is true.
Option (D): In unicellular organisms, reproduction is indeed synonymous with growth, as they both involve a form of cellular division and expansion. Hence, this statement is incorrect.