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

The nucleolus is...

How many chromosomes does a haploid cell of maize contain?

Pars amorpha is associated with

The nucleus is a ....... structure.

Read the following statements $:-$
$(i)$ Centromere is present in the middle of the chromosomes and forms two equal arms.
$(ii)$ Chromosome has a terminal centromere.
$(iii)$ Centromere lies close to the end of the chromosome forming one extremely short and one very long arm.
$(iv)$ Centromere lies slightly away from the middle of the chromosome resulting in one shorter arm and one longer arm.
Select the correct option as per the codes given below $:-$