The answer is the last one (d): First.
Explanation for each option:
a. Fourth: The fourth stage of labor is the period after the delivery of the placenta, typically the first few hours postpartum. This stage involves monitoring the mother for any complications such as hemorrhage. Since the client is still in the process of dilating and has not yet delivered the baby, this option is incorrect.
b. Second: The second stage of labor begins when the cervix is fully dilated (10 cm) and ends with the delivery of the baby. The client in the question is only 6 cm dilated, so this option is incorrect.
c. Third: The third stage of labor starts after the baby is born and ends with the delivery of the placenta. Since the client has not yet delivered the baby, this option is incorrect.
d. First: The first stage of labor is the period from the onset of true labor contractions until the cervix is fully dilated to 10 cm. The client is 6 cm dilated, 75% effaced, and at 0 station, which indicates that she is in the active phase of the first stage of labor. Therefore, this option is correct.
Summary:
The client is experiencing the first stage of labor, as she is 6 cm dilated, 75% effaced, and at 0 station.