What are chromosomes with arms of equal length 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.

Chromosomes can be stained with

The part of the chromosome after the secondary constriction is called ......

Ribosomal $RNA$ is synthesised in

What are nuclear pores? State their function.