Problem:
Question: The following are true about checkpoints in the cell cycle, except:
A) Is a mechanism that can halt cell cycle progression in response to environmental influences
B) Is complex machinery that uses cyclins and cyclin-dependent kinases to regulate cell cycling
C) Occurs only in the middle of the G1 phase of the cell cycle.
D) p53 work as part of a cell cycle checkpoint
E) Rb works as part of a cell cycle checkpoint
Please select correct answer and also provide explaination.