Final answer:
The process by which fluid and solutes are reclaimed from the tubular fluid and returned to the blood in the kidneys is known as tubular reabsorption. It occurs primarily in the proximal convoluted tubule and the loop of Henle.
Step-by-step explanation:
In the kidney, the process by which fluid and solutes from the tubular fluid are reclaimed and returned to the blood is called tubular reabsorption. During this process, substances such as water, glucose, and amino acids that were initially filtered out during glomerular filtration are reabsorbed from the filtrate back into the blood through the efferent arteriole and peritubular capillaries. This reabsorption mainly occurs in the proximal convoluted tubule and the loop of Henle, where a significant amount of solutes and water are reclaimed. In contrast, tubular secretion is the process where substances that the body needs to excrete, like metabolic wastes, urea, uric acid, and certain drugs, are actively secreted into the kidney tubules. This prepares these substances for elimination from the body in the urine. Therefore, the correct answer to the question is 'a. tubular reabsorption.'