The length of a lampbrush chromosome is: (in $\mu m$)

The structure of the nuclear membrane facilitates:

The centromere is also known as $.......$.

$S -$ Assertion: Individual chromosomes are not identifiable during interphase.
$R -$ Reason: They exist as highly extended and elaborate nucleoprotein fibers called chromatin.

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.

During cell division,to which part of the chromosome do the spindle fibers attach?