y does the ocular micrometer need to be calibrated with a stage micrometer?

Question

a. The stage micrometer is a slide that has a defined scale and the distances
between lines don’t change when viewed at different magnifications, unlike
the ocular micrometer.
b. The distance between the lines on the ocular micrometer depends on
magnification and it must be calibrated at every magnification.
c. The distance between the lines on the stage micrometer depends on
magnification and it must be calibrated at every magnification.
d. The stage micrometer is used directly to measure specimens at any
magnification.
e. Both a and b are correct statements.
I said B. Agree?