This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
Free radical injury includes all except? 
Select and explain. 
A. Damaged cell membranes, B. Loss of enzymatic activity, C. Single strand break of DNA, D. Vacuolar degeneration
D: Vacuolar degeneration
Answer: D: Vacuolar degeneration 
Explanation: Cell Injury Caused by Reactive Oxygen Species:
ROS causes cell injury by damaging multiple components of cells.

Lipid peroxidation of membranes. 
Crosslinking and other changes in proteins resulting in enhanced degradation or loss of enzymatic activity.
DNA damage.
In all these cases, cell death may be by necrosis, apoptosis, or the mixed pattern of necroptosis.

The two main morphologic correlates of reversible cell injury are cellular swelling and fatty change.
Microscopic examination may show small, clear vacuoles within the cytoplasm; these represent distended and pinched-off segments of the endoplasmic reticulum (ER). This pattern of non-lethal injury is sometimes called hydropic change or vacuolar degeneration.
Robin’s Textbook of pathology 10th ed Page 45