Correct Answer: A

Rationale: Infection is the most common cause of shock in infants and children due to their increased susceptibility to sepsis. Infants and children have underdeveloped immune systems, making them more prone to infections that can lead to septic shock. While cardiac failure is a serious condition, it is not the most common cause of shock in this population. Accidental poisoning, though dangerous, is less common than infection in causing shock in infants and children. Severe allergic reactions can lead to anaphylactic shock, but they are not as prevalent as infections in causing shock in this age group.

Correct Answer: B

Rationale: The correct answer is B. Myelination occurs in a cephalocaudal (head-to-toe) pattern, improving nerve function progressively. Choice A is incorrect because myelination continues beyond 4 years of age and into adolescence. Choice C is incorrect as myelination speeds up nerve impulses rather than slowing them down. Choice D is incorrect because myelination increases the specificity and efficiency of nerve impulses, making them more focused and precise.

Correct Answer: B

Rationale: The short urethra in young girls is a significant factor that predisposes them to urinary tract infections. Girls have a shorter urethra than boys, making it easier for bacteria to travel up the urinary tract, leading to infections. Increased fluid intake (Choice A) is actually a preventive measure as it helps flush out bacteria from the urinary tract. Prostatic secretions in males (Choice C) do not predispose the urinary tract to infection in children. Frequent emptying of the bladder (Choice D) is also a good practice to prevent urinary tract infections by reducing the chances of bacterial growth in the urinary tract.

Correct Answer: A

Rationale: The correct answer is to 'Eat more food when planning to exercise more than usual.' Increased physical activity requires more energy, so additional food intake is necessary to prevent hypoglycemia. Choice B is incorrect because the method of insulin administration should not be altered based on physical activity. Choice C is incorrect as insulin timing should be consistent rather than based on anticipated exercise. Choice D is incorrect since relying on foods with sugar can lead to unstable blood sugar levels, which is not ideal for managing diabetes during exercise.

Correct Answer: D

Rationale: Mouth breathing due to a cleft lip can dry the mucous membranes, increasing their susceptibility to infection. While waste product accumulation (Choice A) and inadequate circulation (Choice B) may contribute to complications, they are not directly related to infection in this context. Inadequate nutrition (Choice C) may affect overall health but is not the primary reason for infection predisposition in this case.