The optical microscopes used in physicians' office laboratories usually have __________ objectives.

• A. one
• B. ten
• C. six to eight
• D. three or four

Answer: (D)

Verified step by step guidance

1. Understand that the question is about the number of objective lenses typically found on optical microscopes used in physicians' office laboratories.
2. Recall that optical microscopes generally have multiple objective lenses mounted on a rotating nosepiece to provide different magnifications.
3. Recognize that common laboratory microscopes usually have three or four objective lenses, each with different magnification powers (e.g., 4x, 10x, 40x, 100x).
4. Note that the options given (one, ten, six to eight) do not match the typical number of objectives found on these microscopes.
5. Conclude that the correct answer is 'three or four' objectives, as this is the standard configuration for clinical microscopes.