How many chromosomes will the cell have at G1 phase, after the S-phase, and after M-phase respectively, if it has 14 chromosomes at interphase?

The correct option is B 14,14,14
Replication of DNA takes place in the S-phase of the cell cycle. The number of chromosomes reduces only in meiosis. So, the number of chromosomes remain 14, 14 and 14 in G1, after S and M-phase of interphase. After the genetic material is duplicated and condenses during prophase of mitosis, there are still only 14 chromosomes.
First, during the S phase of interphase, the genetic material of a cell is duplicated. So if a cell has 14 chromosomes (a set of 7 you inherit from your mother and a set of 7 from your father). After the genetic material is duplicated and condenses during prophase of mitosis, there are still only 14 chromosomes – however, they exist in a structure that looks like an X shape. These chromatids are genetically identical. However, they are still attached to the centromere and are not yet considered separate chromosomes. Thus, this X shape represents one chromosome, but two chromatids. So, this means that during prophase and metaphase of mitosis, a cell will have 14 chromosomes, but 28 chromatids (again, remember that there are 28 chromatids because the original 14 chromosomes were duplicated during S phase of interphase)