The answer to the question "Reabsorption by the kidney is the process of:" is b-Returning filtered material to the blood stream.

Reabsorption is a crucial process that occurs in the kidneys, which are responsible for filtering the blood and removing waste products from the body. During filtration, water, electrolytes, and other small molecules are removed from the blood and enter the kidney tubules. Reabsorption occurs when the kidney tubules selectively reabsorb these filtered molecules back into the bloodstream, while leaving waste products and excess water to be excreted as urine.

This process is essential for maintaining the body's fluid balance and electrolyte levels, as well as regulating blood pressure and pH. For example, the reabsorption of sodium ions helps to regulate blood pressure, while the reabsorption of glucose and amino acids ensures that these important nutrients are not lost in the urine.

References:

1. Vander's Renal Physiology, 9th edition, by Douglas Eaton and John Pooler
2. Guyton and Hall Textbook of Medical Physiology, 13th edition, by John Hall.