**Core Concept**
The phenomenon of fertilization of a second ovum in a woman who is already pregnant is a rare occurrence that can lead to a complex reproductive situation. This condition is related to the timing of ovulation and fertilization in a woman's menstrual cycle.

**Why the Correct Answer is Right**
When a woman is already pregnant, the fertilization of a second ovum can occur through a process called superfetation. Superfetation is a phenomenon where a second egg is released and fertilized by sperm while the woman is already pregnant with a fertilized egg from a previous ovulation. This can result in the development of two separate embryos, each with its own gestational sac and placenta. Superfetation is a rare occurrence, but it has been documented in some cases.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to the phenomenon of fertilization of a second ovum in a woman who is already pregnant.
* **Option B:** This option refers to a different reproductive concept, where a woman releases multiple eggs at the same time, increasing the chances of multiple pregnancies. However, it does not specifically refer to the fertilization of a second ovum in a woman who is already pregnant.
* **Option C:** This option is a type of multiple pregnancy where two or more eggs are released at the same time and fertilized by sperm, resulting in multiple embryos. While it is a type of multiple pregnancy, it is not specifically related to the fertilization of a second ovum in a woman who is already pregnant.

**Clinical Pearl / High-Yield Fact**
Superfetation is a rare occurrence, but it has been documented in some cases. It is essential for healthcare providers to be aware of this phenomenon, as it can lead to complex reproductive and obstetric situations.

**Correct Answer:** . Superfetation