This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
Fixed time is required for all of the following steps of cell cycle; except 
Select and explain. 
A. S, B. M, C. G1, D. G2
C: G1
Answer: C: G1 
Explanation: •  The time taken for S, G2 and M phases are similar for most cell types, occupying about 6, 4 and 2 hours respectively.
•  The duration of G1 shows considerable variation. It can be as short as 2 hours in rapidly dividing cells like embryonic tissues or as long as 12 hours in some adult tissues.
•  G1 phase is most variable because, in this phase cells are not committed to DNA replication. They can either enter resting state or progress to next cell division.