What are the three main checkpoints during the cell cycle?

I- The first checkpoint occurs at the end of the G1 phase and the beginning of the S phase.
II- The second checkpoint occurs after DNA synthesis.
III- The third checkpoint occurs during metaphase of mitosis.
a) Only I is correct.
b) Only II is correct.
c) Only III is correct.
d) I and II are correct.
e) I, II, and III are correct.