**Core Concept**
Placental separation is a critical step in the process of labor and delivery, characterized by the detachment of the placenta from the uterine wall. This process is accompanied by several clinical signs that indicate the onset of placental separation.

**Why the Correct Answer is Right**
The correct signs of placental separation include the uterus becoming softer, the abdominal girth decreasing, and the umbilical cord prolapsing through the cervix. These changes occur due to the decrease in uterine tone and the loss of placental attachment, allowing for the fetal head to descend and the umbilical cord to protrude. The sensation of a "gush of blood" or a "bloody show" may also be felt as the placenta separates from the uterine wall.

**Why Each Wrong Option is Incorrect**
**Option A:** This option may be a distractor, as it does not clearly relate to the clinical signs of placental separation.
**Option B:** This option could be incorrect, as the sensation of pain and contractions is more related to the process of labor rather than the specific sign of placental separation.
**Option C:** This option might be incorrect, as the presence of fetal distress is more related to the overall health of the fetus rather than a specific sign of placental separation.

**Clinical Pearl / High-Yield Fact**
One key point to remember is that the sensation of placental separation is often accompanied by a decrease in uterine tone, which can be felt as the uterus becomes softer and the abdominal girth decreases. This change in uterine tone is a critical sign that indicates the onset of placental separation.

**Correct Answer:** Not Provided (question was incomplete)