**Core Concept**
Active management of the third stage of labor (AMTSL) is a crucial obstetric intervention aimed at preventing postpartum hemorrhage (PPH). It involves a series of steps to ensure prompt and effective uterine contractions, control bleeding, and prevent complications.

**Why the Correct Answer is Right**
The correct answer involves administering uterotonic agents, such as oxytocin or ergot alkaloids, to stimulate uterine contractions and reduce bleeding. Oxytocin, in particular, works by stimulating the oxytocin receptors on the uterine muscle cells, leading to increased contraction frequency and amplitude. This helps to control bleeding, reduce the risk of PPH, and promote uterine involution.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not specify the administration of uterotonic agents, which is a critical component of AMTSL.
* **Option B:** This option is incorrect because it implies that AMTSL only involves uterine massage, which is not sufficient to prevent PPH.
* **Option C:** This option is incorrect because it suggests that AMTSL is only necessary in cases of PPH, when in fact it is a standard procedure to be followed in all deliveries to prevent PPH.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that AMTSL should be initiated within 1 minute of delivery of the placenta, as delayed uterine contractions can lead to increased bleeding and PPH.

**Correct Answer: D. Administration of uterotonic agents, uterine massage, and controlled cord traction.**