[单选题]
The diagram shows the dominant cyclin/CDK complexes z7 4 ;z.zdsemj(co 82rydkrfq965:fj gfi ;sb at dif(w7g rvh /r+/)ekn0bhqx m( zyferent time points in the cell cycle. Which cyclin/CDK complex activates Dye/qxg7mrhn( z k+/v0w)br h (NA replication machinery?
A. Cyclin A/CDK 2
B. Cyclin B/CDK 1
C. Cyclin D/CDK 4
D. Cyclin A/CDK 1