[单选题]
The diagram shows the dominant cyclin/Cr6 +w 6dsn:gpmnmj)/ ydw7vo4 DK co c g4(* (utmbaohun2q*mplexes at different time points in the cell cycle. Which cyclin/CDK complex activates DNA rep4 o (b um*t*aug(qnc2hlication machinery?
A. Cyclin A/CDK 2
B. Cyclin B/CDK 1
C. Cyclin D/CDK 4
D. Cyclin A/CDK 1