**Core Concept**
Fragile X syndrome is a genetic disorder caused by a mutation in the FMR1 gene on the X chromosome, leading to intellectual disability, physical characteristics, and behavioral problems. It is the most common cause of inherited intellectual disability.

**Why the Correct Answer is Right**
Pigmented nevi, also known as congenital melanocytic nevi, are not a characteristic feature of Fragile X syndrome. In fact, Fragile X syndrome is often associated with a variety of physical features, including a long face, large ears, a prominent jaw, and macroorchidism (large testes) in males after puberty. The presence of pigmented nevi is not a typical finding in Fragile X syndrome.

**Why Each Wrong Option is Incorrect**
**Option A:** Large testis is actually a characteristic feature of Fragile X syndrome, particularly in males, due to the development of macroorchidism after puberty.
**Option C:** Large ear present is also a common feature of Fragile X syndrome, often described as a prominent or large ear.
**Option D:** No large nose is incorrect because Fragile X syndrome is often associated with a narrow palate and a long face, but not specifically with a large nose.

**Clinical Pearl / High-Yield Fact**
Fragile X syndrome is caused by an expansion of the CGG repeat in the FMR1 gene, leading to methylation and silencing of the gene. This results in the absence of the FMRP protein, which is essential for normal brain development and function.

**✓ Correct Answer: B. Pigmented nevi**