Which of the following statements about nuclear genome organization is CORRECT?

A．Centromeres are sequences located at the ends of each chromosome.
B．Nucleolar organizer regions are portions of chromosomes where ribosomal RNA genes are clustered and transcribed.
C．Telomeres are where sister chromatids adhere to each other and where spindle fibers attach during cell division.
D．Chromosome organization is random in the interphase nucleus.