Cells start to divide when they receive a signal. They continue to divide until they get another signal to stop. A cell with damaged DNA may not respond to the stop signal. The cell can become cancerous and divide uncontrollably. The cancerous cell and all its daughter cells can form a tumor. During which step of the cell cycle does a cell get a signal to begin cell division?

Prophase.

Explanation:

Prophase is the stage of cell cycle which receive the signal to start cell division. Due to this signal, the nucleus dissolves inside the cell and the chromosomes begin movement to the middle line of the cell where these chromosomes condenses and then division of the cell occurs in later steps of mitosis cell division. So we can conclude that prophase step started when it got signal.

b is the answer and if you need further with anything message me