What is the disc-shaped structure present on the centromere of each chromosome called?

Which of the following statements is/are correct?
$(a)$ The nuclear matrix or nucleoplasm contains the nucleolus and chromatin.
$(b)$ The outer nuclear membrane $(Ectokaryotheca)$ is usually continuous with the endoplasmic reticulum and also bears ribosomes on it.
$(c)$ Cells that are actively synthesizing protein have small and fewer nucleoli.

What can be observed in the interphase nucleus using a light microscope?

Which of the following is enucleate?

What happens if the nucleus is removed from a cell?

Chromatin is made up of: