Which phase of the cell cycle is the least common process of mitosis and what could be the reason?

In anaphase, the shortest stage of mitosis, the sister chromatids break apart, and the chromosomes begin moving to opposite ends of the cell. By the end of anaphase, the 2 halves of the cell have an equivalent collection of chromosomes. In telophase, 2 daughter nuclei form. The nuclear envelope beings to reappear.

for a different answer set the answer would be because the oxygen in the water had depleted (apex)