To answer the given question, we need to evaluate both the assertion and the reason:

1. Assertion (A): In chronic renal failure, the glomerular filtration rate (GFR) falls to less than 15 ml/min.
   • This statement is accurate. In chronic renal failure, especially in its advanced stage known as end-stage renal disease (ESRD), the GFR falls to below 15 ml/min. This is a critical threshold indicating severe kidney function impairment.
2. Reason (R): The chronic renal failure patients are recommended diets high in protein and sodium.
   • This statement is incorrect. High protein and sodium diets are generally not recommended for chronic renal failure patients. In fact, these patients are often advised to follow a low-protein diet to reduce kidney workload and a low-sodium diet to manage blood pressure and fluid balance.

Since Assertion (A) is correct and Reason (R) is incorrect, the correct code is:

• (A) is correct and (R) is incorrect

Thus, the reasoning behind this choice is that while the assertion correctly describes a characteristic of chronic renal failure, the suggested dietary recommendations mentioned in the reason are incorrect for managing the condition.