The correct answer is c - Concentrated urine.

Osmolality is a measure of the concentration of solutes in a solution, and in the case of urine, it refers to the concentration of electrolytes, urea, and other solutes. High osmolality of urine indicates that the concentration of solutes in the urine is high, which means that the urine is concentrated.

This can be caused by a number of factors, including dehydration, excessive sweating, and certain medical conditions such as diabetes insipidus. When the body is dehydrated, the kidneys will conserve water by producing concentrated urine. In contrast, when the body is well hydrated, the kidneys will produce dilute urine.

It is important to note that high osmolality of urine is not a reliable indicator of renal kidney disease. Other tests, such as blood tests and imaging studies, are needed to diagnose kidney disease.

References:
1. Rose BD, Post TW. Clinical Physiology of Acid-Base and Electrolyte Disorders. 5th ed. New York: McGraw-Hill Medical; 2001.
2. Skorecki K, Chertow GM, Marsden PA, Taal MW, Yu ASL, eds. Brenner and Rector's The Kidney. 10th ed. Philadelphia: Elsevier; 2016.