Linked genes
a. are found on homologous chromosomes.
b. never cross over during prophase
c. undergo crossing-over of sister chromatids at a high rate.
d. tend to be close together on a single chromosome.
e. always assort independently.

Option D.

Explanation:

the diploid number of chromosomes is sometimes represented by the symbol 2n. for the fruit fly, the diploid number is 8, which can be written as 2n = 8, where n represents twice the number of chromosomes in a sperm or egg cell.