Final answer:
An abnormal drop in ejection fraction (EF) from rest to stress is considered to be greater than 15%.
Step-by-step explanation:
The normal range for ejection fraction (EF) is approximately 55-70 percent, with a mean of 58 percent. An abnormal drop in EF from rest to stress is generally considered to be greater than 15%. Therefore, the correct answer is D) >15%.