Final answer:
An exercise test should be terminated at level 2 out of 4 (moderate, bothersome) for angina, to prevent the condition from worsening to unstable angina, which is a medical emergency.
Step-by-step explanation:
An exercise test should be terminated at a level of angina that is moderate, or 2 out of 4 on the severity scale, which is described as bothersome. Waiting until angina is severe or most severe could put the patient at increased risk. Stable angina may worsen and become unstable angina, especially under the stress of exercise, which poses a significant risk and requires urgent medical attention. Therefore, the answer to the question is that an exercise test should be terminated when angina reaches a 2 out of 4 severity level.