........................... represents the most active stage of the cell cycle.

Given below are the two statements.
Statement $I$: Replication of $DNA$ occurs in the '$S$' phase of interphase in the cell cycle.
Statement $II$: Replication of $DNA$ takes place only once in the cell cycle.
In the light of above statements,choose the correct answer from the options given below:

In the given diagram,what does $G$ represent?

Which important metabolic process occurs during the interphase between two successive cell divisions?

In which of the following cells is the cell cycle completed in $90$ minutes?

After which phase does the cell enter mitosis?