The vertebrate kidney helps to keep the acidity of the body fluids constant by varying the amount of hydrogen ions it secretes into the urine. You can confidently predict that this aspect of kidney function would be controlled by

Hypothalamus

You can confidently predict that this aspect of kidney function would be controlled by hypothalamus

Explanation:

Hypothalamus is the part of the brain found just below the thalamus. It plays an important role in homeostasis i.e maintaining balance of water and electrolyte in the body.

The amount of electrolyte such as hydrogen ions in the body is controlled by the hypothalamus, when it stimulate the kidney to excrete excess hydrogen ions through urine, or retain hydrogen ions from urine.

Thus, hypothalamus is the answer

the generally accepted parts of modern cell theory include: all known living things are made up of one or more cells. all living cells arise from pre-existing cells by division. the cell is the fundamental unit of structure and function in all living organisms.