**Core Concept**
The corpus luteum is a temporary endocrine structure in the female ovaries that plays a crucial role in the menstrual cycle and early pregnancy. It forms after ovulation and secretes progesterone to prepare the uterus for a potential pregnancy. The corpus luteum is essential for maintaining pregnancy until the placenta takes over its function.

**Why the Correct Answer is Right**
The correct answer is related to the functions of the corpus luteum. The corpus luteum secretes progesterone, which is essential for preparing the uterus for implantation of the fertilized egg. Progesterone also maintains the endometrium during early pregnancy. The corpus luteum also produces estrogen, which helps maintain the endometrial growth and prepares it for implantation.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not relate to the corpus luteum. The corpus luteum is not involved in the production of follicle-stimulating hormone (FSH).
**Option B:** This option is incorrect because it is a function of the placenta, not the corpus luteum. The placenta takes over the production of estrogen and progesterone during the second trimester of pregnancy.
**Option C:** This option is incorrect because it is a function of the adrenal glands, not the corpus luteum. The adrenal glands produce aldosterone, which is involved in the regulation of electrolyte balance.

**Clinical Pearl / High-Yield Fact**
The corpus luteum is essential for maintaining pregnancy until the placenta takes over its function. The corpus luteum forms after ovulation and secretes progesterone to prepare the uterus for a potential pregnancy.

**Correct Answer: D.**