Correct Answer: D

Rationale: Excessive vomiting in pyloric stenosis leads to the loss of stomach acid (hydrochloric acid), resulting in metabolic alkalosis, not hyperkalemia, hyperchloremia, or metabolic acidosis. Metabolic alkalosis is characterized by a higher pH level in the blood due to the loss of acid and a relative increase in bicarbonate. Hyperkalemia is an elevated level of potassium in the blood and is not directly related to excessive vomiting in pyloric stenosis. Hyperchloremia is an excess of chloride in the blood, which is not typically associated with this condition. Metabolic acidosis is a condition characterized by a lower pH level in the blood, caused by an excess of acid or a loss of bicarbonate, which is not the typical complication seen in pyloric stenosis with excessive vomiting.

Correct Answer: B

Rationale: The correct answer is B: Encourage oral rehydration. Oral rehydration is the first-line treatment for moderate dehydration in children. It helps restore fluid balance and electrolyte levels. Administering IV fluids (Choice A) is usually reserved for severe cases of dehydration where oral rehydration is not feasible or ineffective. Monitoring vital signs (Choice C) is important but should not replace the immediate need for rehydration. Providing clear fluids (Choice D) may not contain the necessary electrolytes required for effective rehydration.

Correct Answer: A

Rationale: A 'strawberry tongue' is a characteristic finding in Kawasaki disease. The presence of a 'strawberry tongue' is a classic sign of Kawasaki disease, along with other features such as conjunctivitis and rash. Choice B, polyarthritis, is not typically seen in Kawasaki disease. Choice C, hematuria, is not a common finding in Kawasaki disease but may be seen in other conditions. Choice D, rashes, are present in Kawasaki disease but are not as specific or characteristic as the 'strawberry tongue'. Therefore, the correct answer is A.

Correct Answer: A

Rationale: Polyarthritis is indeed frequently the initial sign of acute rheumatic fever in children. It presents as joint pain, swelling, and redness. Carditis (inflammation of the heart), Erythema marginatum (a skin rash), and Sydenham chorea (involuntary muscle movements) are typically seen in the later stages of acute rheumatic fever and not as the initial sign.

Correct Answer: A

Rationale: Handwashing is indeed the most effective way to prevent the spread of hand, foot, and mouth disease in children. Proper hand hygiene helps in removing and killing germs that can cause infections. While isolating sick children and disinfecting toys are important measures to prevent the spread of diseases, they are not as effective as handwashing. Encouraging vaccination, in this case, is not relevant since there is no specific vaccine available for hand, foot, and mouth disease.