The core concept of this question is to understand the term related to computer-generated imagery that has reached the level of being indistinguishable from reality. The correct answer is 'C. Indistinguishability' because it directly refers to the inability to tell the difference between a computer-generated image and a real one. 'A. Realism' could be misleading as it relates to the quality of being realistic but does not necessarily imply indistinguishability. 'B. Perfection' is incorrect because it suggests an ideal state without imperfections, which is not the focus of the question. 'D. Clarity' refers to the quality of being clear or easily visible, which is not related to the concept of being indistinguishable from reality.