The second stage of labor begins and ends with which events?

Correct option is B

Second stage of labor = from full cervical dilation (10 cm) until delivery of the fetus.
Explanation of options: (a) ✘ This describes first stage (latent + active). (b) ✔ Correct; fully dilated cervix to birth = second stage. (c) ✘ Delivery of placenta is third stage. (d) ✘ Involution is puerperium, not labor stage.