Answer :
Ans.
Mitosis is a type of cell division, during which a single parent cell gives rise to two daughter cells, having half number and amount of genetic material as parent cell. The blue-tongued blue fish is an eukaryotic diploid organism, means it has two sets of chromosomes (2n, where n is the number of chromosomes).
Before mitosis, DNA gets replicated and becomes double during Synthesis or S phase. As the blue fish is about to undergo mitosis and its DNA has been replicated, it will show 2n = 4 chromosomes and at the end of mitosis, each resulting cell will receive half of the number of chromosomes, that is, 2n.
Thus, the correct answer is '2n = 4.'