Final answer:
Diabetic clients should have their toenails trimmed by a medical doctor due to the increased risk of complications such as infections and ulcers.
Step-by-step explanation:
The question regarding which types of clients should have their toenails trimmed only by a MD is specifically related to healthcare and patient safety. Among the listed options, diabetic clients need special foot care and should generally have their toenails trimmed by a healthcare professional such as a podiatrist or other medical doctor (MD) to prevent complications such as infections ulcers or even gangrene due to their heightened risk resulting from often reduced blood flow and neuropathy.
While the elderly may also benefit from professional care it is not exclusive that they must have it done only by an MD hypertensive and athletes are not in the categories that specifically require an MD for toenail trimming unless there are other risk factors present.