Question

what does the revolving nosepiece hold in the microscope?
the ocular
the condenser
the diaphragm
the oil immersion objective

Explanation:

The revolving nosepiece of a microscope is the rotating component that holds objective lenses. The oil immersion objective is a type of objective lens, while the ocular is the eyepiece (separate from the nosepiece), the condenser and diaphragm are part of the microscope's lower optical system, not held by the nosepiece.

Answer:

The oil immersion objective