Final answer:
Option c is a correctly written example of an actual nursing diagnosis that identifies activity intolerance and provides evidence of oxygen imbalance and related symptoms.
Step-by-step explanation:
The correct example of an actual nursing diagnosis is option c. Activity intolerance related to imbalance between oxygen supply and demand as evidenced by dyspnea on exertion and significant drop of oxygen saturation from 98% to 88% with activity. This statement clearly identifies the nursing diagnosis of activity intolerance and provides evidence of oxygen imbalance and symptoms experienced by the patient.