Final answer:
Atherosclerosis refers to fixed coronary obstruction. It occurs when plaque builds up in the coronary arteries, blocking or narrowing them and impeding blood flow to the heart. This can lead to a myocardial infarction or heart attack.
Step-by-step explanation:
The fixed coronary obstruction referred to in the question is A. Atherosclerosis. Atherosclerosis is a condition that occurs when plaque builds up in the coronary arteries, causing them to become blocked or narrowed. This obstructs blood flow to the heart and can lead to decreased blood flow (ischemia) and insufficient oxygen (hypoxia) delivered to the cardiac tissues, which can ultimately result in a myocardial infarction or heart attack.