Correct Answer: D

Rationale: Producing phosphate buffers is not the main function of the kidneys in response to acid-base disturbances. Phosphate buffers are mainly found in the intracellular fluid and the urine, where they help to maintain the pH by binding or releasing hydrogen ions. Adjusting PaCO2 levels is not the function of the kidneys, but rather the function of the lungs in response to acid-base disturbances. The lungs regulate the PaCO2 levels by increasing or decreasing the rate and depth of respiration, which affects the amount of carbon dioxide exhaled. Producing protein buffers is not the function of the kidneys, but rather the function of the cells and the plasma in response to acid-base disturbances. Protein buffers are the most abundant and versatile buffers in the body, as they can act as acids or bases by donating or accepting hydrogen ions. Excreting or reabsorbing hydrogen or bicarbonate is the main function of the kidneys in response to acid-base disturbances. The kidneys regulate the HCO3- levels by either reabsorbing it from the filtrate or generating it from carbon dioxide and water. The kidneys also regulate the hydrogen ion levels by either excreting it into the urine or exchanging it for sodium ions.

Correct Answer: D

Rationale: Stroke is not a cause of hyponatremia, but rather a possible complication of it. Hyponatremia is a condition where the sodium level in the blood is too low, which can affect the brain function and cause symptoms such as confusion, seizures, or coma. Stroke is a condition where the blood supply to a part of the brain is interrupted, which can cause brain damage and neurological deficits. Dehydration is not a cause of hyponatremia, but rather a cause of hypernatremia. Dehydration is a condition where the body loses more fluids than it takes in, which can affect the blood volume and the electrolyte balance. Dehydration can cause hypernatremia, which is a condition where the sodium level in the blood is too high, which can also affect the brain function and cause symptoms such as thirst, dry mouth, or lethargy. Increased secretion of aldosterone is not a cause of hyponatremia, but rather a cause of hypokalemia. Aldosterone is a hormone that regulates the sodium and potassium levels in the body by increasing the reabsorption of sodium and the excretion of potassium in the kidneys. Increased secretion of aldosterone can cause hypokalemia, which is a condition where the potassium level in the blood is too low, which can affect the muscle and nerve function and cause symptoms such as weakness, cramps, or arrhythmias. Congestive heart failure (CHF) is a cause of hyponatremia, as it is a condition where the heart is unable to pump enough blood to meet the body's needs. This can lead to fluid retention and edema, which can dilute the sodium level in the blood and cause hyponatremia. CHF can also stimulate the release of antidiuretic hormone (ADH), which increases the reabsorption of water in the kidneys and further lowers the sodium level in the blood.

Correct Answer: D

Rationale: Producing phosphate buffers is not the main function of the kidneys in response to acid-base disturbances. Phosphate buffers are mainly found in the intracellular fluid and the urine, where they help to maintain the pH by binding or releasing hydrogen ions. Adjusting PaCO2 levels is not the function of the kidneys, but rather the function of the lungs in response to acid-base disturbances. The lungs regulate the PaCO2 levels by increasing or decreasing the rate and depth of respiration, which affects the amount of carbon dioxide exhaled. Producing protein buffers is not the function of the kidneys, but rather the function of the cells and the plasma in response to acid-base disturbances. Protein buffers are the most abundant and versatile buffers in the body, as they can act as acids or bases by donating or accepting hydrogen ions. Excreting or reabsorbing hydrogen or bicarbonate is the main function of the kidneys in response to acid-base disturbances. The kidneys regulate the HCO3- levels by either reabsorbing it from the filtrate or generating it from carbon dioxide and water. The kidneys also regulate the hydrogen ion levels by either excreting it into the urine or exchanging it for sodium ions.

Correct Answer: C

Rationale: One slice of wheat bread is not the best source of potassium, as it contains only about 70 mg of potassium per serving. The recommended daily intake of potassium for adults is 4,700 mg. One wedge of cantaloupe is a good source of potassium, as it contains about 430 mg of potassium per serving. However, it is not the best source of potassium among the choices given. One banana is the best source of potassium among the choices given, as it contains about 420 mg of potassium per serving. Bananas are also rich in fiber, vitamin C, and antioxidants. One slice of cheddar cheese is not the best source of potassium, as it contains only about 28 mg of potassium per serving. Cheese is also high in sodium, fat, and calories, which can have negative effects on blood pressure and cholesterol levels.

Correct Answer: A

Rationale: Diffusion is the process by which small ions such as glucose, oxygen, and carbon dioxide redistribute themselves through semipermeable membranes from areas of higher concentration to areas of lower concentration. This is how these molecules move across the cell membrane and the capillary wall. Osmosis is the process by which water moves through semipermeable membranes from areas of lower solute concentration to areas of higher solute concentration. This is how water balance is maintained across the cell membrane and the capillary wall. Blood pressure is the force exerted by the blood on the walls of the blood vessels. It is not a process by which small ions redistribute themselves through semipermeable membranes, but rather a factor that influences the movement of fluids and solutes across the capillary wall. Rehydration is the process of restoring the fluid balance in the body by drinking fluids or receiving intravenous fluids. It is not a process by which small ions redistribute themselves through semipermeable membranes, but rather a treatment for dehydration.