Final answer:
When a patient's systolic blood pressure falls more than 10 mmHg during exercise, the ACSM recommends immediately stopping the test to address potential cardiovascular concerns.
Step-by-step explanation:
If a patient's systolic blood pressure drops more than 10 mmHg during exercise, according to the American College of Sports Medicine (ACSM), the correct action to take is to immediately stop the test (Option C).
This drop could indicate an underlying cardiovascular problem that requires immediate attention. A significant drop in systolic blood pressure during exercise is not a normal response and could signify a hemodynamic issue that might necessitate medical evaluation.