In this disease, there occurs a failure of chloride ion transport mechanism in cell surface membrane of epithelial cells, Sweat of the patient contains very high level of `Na^(+)` and `Cl^(-)` ions. The disease is

Options

A. (a) thalassaemia
B. (b) Alzheimer's disease
C. (c) Gaucher's disease
D. (d) cystic fibrosis

Explanation

To solve the question regarding the disease characterized by a failure of chloride ion transport in epithelial cells, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Symptoms**: The question states that there is a failure of chloride ion transport in the cell surface membrane of epithelial cells and that the sweat of the patient contains very high levels of sodium (Na⁺) and chloride (Cl⁻) ions.

2. **Identify the Key Features**: The key features to note are:
- Failure of chloride ion transport mechanism.
- High levels of Na⁺ and Cl⁻ in sweat.

3. **Review the Options**: The options provided include:
- Thalassemia
- Alzheimer’s disease
- Gaucher’s disease
- Cystic fibrosis

4. **Analyze Each Option**:
- **Thalassemia**: This is a blood disorder related to hemoglobin production and does not relate to chloride ion transport.
- **Alzheimer’s Disease**: This is a neurodegenerative disorder affecting memory and cognition, not related to chloride transport.
- **Gaucher’s Disease**: This is a metabolic disorder due to enzyme deficiency, not related to chloride ion transport.
- **Cystic Fibrosis**: This is a genetic disorder that affects the lungs and digestive system due to a deficiency of the CFTR (Cystic Fibrosis Transmembrane Conductance Regulator) protein, leading to abnormal regulation of chloride and sodium ions.

5. **Conclusion**: Based on the analysis, the disease that matches the description of chloride ion transport failure and high levels of sodium and chloride in sweat is **Cystic Fibrosis**.

### Final Answer:
The disease is **Cystic Fibrosis**.