**Core Concept**
Hanup's disease, also known as Hartnup disease, is a rare genetic disorder affecting the metabolism of certain amino acids. It is characterized by impaired renal reabsorption of neutral amino acids, leading to their excessive excretion in the urine.

**Why the Correct Answer is Right**
In Hanup's disease, there is a defect in the SLC6A19 gene, which encodes for a neutral amino acid transporter in the kidneys. This transporter plays a crucial role in the reabsorption of neutral amino acids, such as tryptophan, leucine, and isoleucine, from the filtrate in the renal proximal tubules. As a result, these amino acids are instead excreted in the urine, causing a range of clinical symptoms, including pellagra-like skin rash, neurological abnormalities, and other systemic manifestations.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to Hanup's disease, which is characterized by the impaired reabsorption of neutral amino acids, not acidic or basic amino acids.
* **Option B:** This option is incorrect as it does not relate to the primary defect in Hanup's disease, which is the impaired reabsorption of neutral amino acids.
* **Option C:** This option is incorrect as it does not accurately describe the primary defect in Hanup's disease, which is the impaired reabsorption of neutral amino acids, not the excessive reabsorption of glucose.

**Clinical Pearl / High-Yield Fact**
Hanup's disease is a rare but important condition to recognize, as it can present with a range of systemic symptoms, including pellagra-like skin rash, neurological abnormalities, and other manifestations. The diagnosis is often made through urinary amino acid analysis, which reveals an excessive excretion of neutral amino acids.

**Correct Answer: B. Neutral amino acids.**