Answer
      The correct option is C.
Reason
      Each option is explained with reason which is given below.
Option A
       It is incorrect because chromatid is the identical copy of chromosome which is formed during DNA replication. It appears to be an arm of chromosome. Â
Option B
        It is incorrect because paired chromosomes that have genes arranged in the same order are known as homologous chromosomes.
Option C
       It is correct option because the part of a chromosome that joins the sister chromatids is known as centromere. It contains a disc shape protein called kinetochore. It is that region where spindle fibers attach during mitosis and is responsible for actual movement of chromosomes during segregation. Â
Option D
       It is incorrect because the material that makes up a chromosome is composed of DNA and proteins. DNA is a polymer of nucleotide monomers. Each nucleotide is composed of:
1. Pentose sugar
2. nitrogenous base, and
3. phosphoric acid
While protein of chromosome is known as histone proteins. The DNA and protein combine to form chromatin a thread like structure which is about 31 cm in human diploid cell. Â This chromatin is then packed up to make nucleosome. In mammalian cells about 2mm DNA wrapped around eight histone proteins to make a nucleosome unit. The nucleosomes are then packaged up to make chromosome
Conclusion
         Thus the correct option is C.
