Which organelle is known as the control center of the cell?

The "master mind" of the cell is

Select the correct option for the following matches:

Column-$I$	Column-$II$
$(1)$ Chromosome arms are of equal length	$(a)$ Submetacentric
$(2)$ One arm of the chromosome is shorter	$(b)$ Acrocentric
$(3)$ One arm is extremely long and the other is very short	$(c)$ Telocentric
$(4)$ Terminal centromere	$(d)$ Metacentric

The common point of attachment of all the arms of polytene chromosome is known as

Which of the following are used to define the karyotype of a species?
$1$. The number of chromosomes
$2$. The chromosome length
$3$. The positions of the centromeres

Which of the following is actively involved in the synthesis of ribosomal $RNA$?