Correct Answer: A

Rationale: Narrow, peaked T waves are a sign of hyperkalemia, which is a high level of potassium in the blood. Potassium is an electrolyte that affects the electrical activity of the heart. Hyperkalemia can cause the T waves, which represent the repolarization of the ventricles, to become narrow and peaked, indicating a rapid and excessive repolarization. ST elevation is a sign of myocardial infarction, which is a heart attack. It indicates that the myocardium, or the heart muscle, is damaged and deprived of oxygen. ST elevation is not related to the potassium level, but rather to the coronary artery blood flow. Peaked P waves are a sign of atrial hypertrophy, which is an enlargement of the atria, the upper chambers of the heart. It indicates that the atria are under increased pressure or workload. Peaked P waves are not related to the potassium level, but rather to the atrial function. Prominent U waves are a sign of hypokalemia, which is a low level of potassium in the blood. Potassium is an electrolyte that affects the electrical activity of the heart. Hypokalemia can cause the U waves, which represent the repolarization of the Purkinje fibers, to become prominent and visible, indicating a delayed and prolonged repolarization.

Correct Answer: C

Rationale: This is incorrect because diffusion is the movement of solutes (dissolved substances) from an area of higher concentration to an area of lower concentration, until equilibrium is reached. This is incorrect because hydrostatic pressure is the force exerted by a fluid against a wall or a membrane. Hydrostatic pressure can drive the movement of fluid and solutes across a membrane, but it is not the movement itself. This is correct because osmosis is the movement of a pure solvent (liquid) across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration, until equilibrium is reached. This is incorrect because ATP is not a movement, but a molecule. ATP stands for adenosine triphosphate, which is the main source of energy for cellular processes. ATP can provide energy for some types of transport across membranes, such as active transport.

Correct Answer: B

Rationale: This is incorrect because 120 to 140 mEq/L is a low range for serum sodium, which indicates hyponatremia. Hyponatremia can cause confusion, lethargy, seizures, and coma. This is correct because 135 to 145 mEq/L is the normal range of serum sodium in adults. Sodium is essential for fluid balance, nerve transmission, and muscle contraction. This is incorrect because 150 to 160 mEq/L is a high range for serum sodium, which indicates hypernatremia. Hypernatremia can cause thirst, dry mouth, agitation, and convulsions. This is incorrect because 165 to 175 mEq/L is a very high range for serum sodium, which indicates severe hypernatremia. Severe hypernatremia can cause irreversible brain damage and death.

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.