Total magnification is eyepiece times objective.

Steps:

• Calculate A: 5 × 100 = 500×.
• Calculate B: 10 × 40 = 400×.
• Calculate C: 10 × 100 = 1000×.
• Calculate D: 15 × 100 = 1500×.

Why D is correct:

• Total magnification equals eyepiece magnification multiplied by objective magnification; D yields 1500×, the highest value.

Why the others are wrong:

• A: Produces only 500×, far below D.
• B: Yields 400×, the lowest total.
• C: Gives 1000×, less than D's 1500×.

Final answer: D