What part of the microscope holds and allows selection of the objective lenses?

The nosepiece is a crucial component of a microscope that holds the objective lenses and allows the user to rotate between them. This functionality is vital, as different objective lenses provide varying levels of magnification, enabling the user to observe specimens with appropriate detail and clarity.

By rotating the nosepiece, the user can easily switch from low magnification for a broader view of the specimen to higher magnification for a detailed examination. This flexibility is essential for effective microscopy, as it allows for a comprehensive understanding of the samples being studied.

In contrast, the base supports the entire microscope and provides stability. The stage is where the specimen slide is placed for observation, while the eyepiece is the part through which the viewer looks to see the magnified image, but it does not have any role in selecting or holding the objective lenses.