What does $S$ represent in the given diagram?

Which of the following terms is consistent with the statement: '$A$ series of events occurring within a cell that leads to cell division and duplication of the cell'?

In which phase are cells biosynthetically active but unable to divide?

What is the average cell cycle span for a mammalian cell?

Which phase of interphase is the most important point in regulation of the cell cycle,during which it must decide whether the cell will start a new cycle or will enter in $G_0$ phase?

Which of the following is true for the $S$ phase of the cell cycle?