**Core Concept**
Laurence Moon Biedl syndrome, also known as Bardet-Biedl syndrome, is a rare genetic disorder that affects multiple organ systems and is characterized by a combination of physical and developmental abnormalities. The syndrome is caused by mutations in genes involved in ciliary function and is inherited in an autosomal recessive pattern.

**Why the Correct Answer is Right**
The correct answer is **B. Asthenic built** because Laurence Moon Biedl syndrome is typically associated with obesity, not asthenic (thin or slender) build. The syndrome is characterized by a range of physical features, including obesity, intellectual disability, polydactyly, hypogonadism, and renal anomalies. The obesity in Laurence Moon Biedl syndrome is due to hyperphagia and insulin resistance, which are thought to be related to the impaired function of cilia in the hypothalamus.

**Why Each Wrong Option is Incorrect**
**Option A:** Digital anomaly is a common feature of Laurence Moon Biedl syndrome, with polydactyly (extra fingers or toes) being a characteristic finding.
**Option C:** Mental retardation is a common feature of Laurence Moon Biedl syndrome, with most affected individuals having intellectual disability.
**Option D:** Hypogonadism is a common feature of Laurence Moon Biedl syndrome, with affected individuals often having delayed or absent puberty.

**Clinical Pearl / High-Yield Fact**
Laurence Moon Biedl syndrome is a ciliopathy, meaning that it is caused by impaired function of cilia, which are microtubule-based structures that play a critical role in the development and function of many organs.

**✓ Correct Answer: B. Asthenic built**