Answer: Option C When each chromosome has been duplicated.
Step-by-step explanation:
- The S phase is the synthesis phase of the cell cycle.
- The S phase occurs between G1 and G2 phase.
- The main process that takes place in the cell during the S phase is DNA replication.
- For DNA replication to take place, it is necessary for each chromosome to be duplicated only then we can say that DNA replication is complete.
Thus, we say that S phase is complete when each chromosome has been duplicated.