## Core Concept
Inhibin-A is a protein complex that plays a crucial role in the regulation of the reproductive cycle, particularly in the feedback inhibition of follicle-stimulating hormone (FSH) secretion from the anterior pituitary gland. It is a member of the transforming growth factor-beta (TGF-β) superfamily. Inhibin-A is produced by the granulosa cells in the ovaries of females and by the Sertoli cells in the testes of males.

## Why the Correct Answer is Right
The correct answer, , indicates that Inhibin-A is produced by the placenta. During pregnancy, the placenta produces Inhibin-A, which can be used as a marker in prenatal screening tests for Down syndrome and other chromosomal abnormalities. The production of Inhibin-A by the placenta is a critical aspect of its role in pregnancy and fetal development.

## Why Each Wrong Option is Incorrect
- **Option A:** This option is incorrect because, although granulosa cells do produce inhibin-A in females, the question seems to be pointing towards a more specific context given the correct answer.
- **Option B:** This option is incorrect because Sertoli cells produce inhibin-B, not Inhibin-A, in males.
- **Option C:** This option might seem plausible due to the role of granulosa cells, but given the context of the correct answer, it does not align.

## Clinical Pearl / High-Yield Fact
A key point to remember is that maternal serum Inhibin-A levels are used in the second trimester as part of the quad screen (quadruple marker test) to screen for Down syndrome, trisomy 18, and open neural tube defects. Elevated levels of Inhibin-A are associated with an increased risk of Down syndrome.

## Correct Answer: D. Placenta.