Which statement about Giardia lamblia cysts is true?

• A. They are round and 2 μm
• B. They are cylindrical and 20 μm
• C. Oval to ellipsoid, about 8–12 μm, with four nuclei in mature cysts
• D. They are spherical with eight nuclei

Answer: (C)

Giardia lamblia cysts are the infectious form that you’d identify under the microscope by their distinctive morphology. They are oval to ellipsoid in shape, about 8–12 micrometers long, and in mature cysts they contain four nuclei. This combination—oval to ellipsoid shape, a size in the 8–12 μm range, and four nuclei—is characteristic of Giardia cysts and helps distinguish them from other protozoan cysts or incorrect descriptions. The other statements don’t fit because the cysts are not small round bodies (2 μm), not cylindrical and 20 μm, and not spherical with eight nuclei.