**Core Concept**
Testosterone and dihydrotestosterone (DHT) are the primary androgens produced by Leydig cells in the testis, playing crucial roles in male development and reproductive functions. Leydig cells are responsible for the production of androgens in response to luteinizing hormone (LH) stimulation.

**Why the Correct Answer is Right**
The correct answer is **estriol**. Estriol is an estrogen, not an androgen, and is predominantly produced in the placenta during pregnancy. Leydig cells produce testosterone through the action of the enzyme cholesterol desmolase, which converts cholesterol into pregnenolone, which is then further converted into androgens. Estriol is not produced by Leydig cells and is not an androgen.

**Why Each Wrong Option is Incorrect**
**Option A:** Testosterone is a primary androgen produced by Leydig cells, making it the correct answer, so we'll skip discussing it here.
**Option B:** Dihydrotestosterone (DHT) is a potent androgen produced by Leydig cells through the action of the enzyme 5-alpha-reductase, which converts testosterone into DHT. It plays a crucial role in male development and reproductive functions.
**Option D:** Androstenedione is an androgen produced by Leydig cells and is a precursor to testosterone.

**Clinical Pearl / High-Yield Fact**
Leydig cells are also known as interstitial cells of Leydig, and their dysfunction can lead to hypogonadism, characterized by low testosterone levels and impaired reproductive functions.

**Correct Answer:** D. Estriol.