Final answer:
The nurse identifies the client is in the Transition phase of labor when the cervix is 9cm dilated. This phase is the final part of the first stage of labor and is characterized by strong and intense contractions.
Step-by-step explanation:
The nurse identifies the client is in the Transition phase of labor when the cervix is 9cm dilated. The transition phase is the final part of the first stage of labor, which begins when the cervix is around 8-10cm dilated and ends when it is fully dilated at 10cm. During this phase, contractions become stronger, closer together, and more intense as the cervix continues to dilate.