Correct Answer: C

Rationale: H. pylori is the most common microorganism associated with gastritis, present in over 80% of cases. While syphilis, cytomegalovirus, and mycobacterium can also cause gastritis, they are much less prevalent compared to H. pylori. Therefore, the correct answer is H. pylori.

Correct Answer: C

Rationale: The correct answer is 22 gauge. A 22-gauge needle is recommended for school-age children, toddlers, and adolescents due to their muscle mass and tolerance. In infants, a smaller gauge (23-25) is preferred as their muscles are less developed and more sensitive. Choice A, 27 gauge, is too thin for an intramuscular injection in a 12-year-old boy. Choice B, 25 gauge, is more suitable for infants than for a 12-year-old. Choice D, 20 gauge, is too thick and not typically used for intramuscular injections in children.

Correct Answer: C

Rationale: Choice C is indicative of a tension pneumothorax, which is considered a medical emergency. The respiratory system is severely compromised, and venous return to the heart is affected. The mediastinal shift is to the unaffected side, indicating a critical situation that requires immediate intervention to prevent further deterioration. This condition can rapidly progress to a life-threatening state, necessitating prompt medical attention. Choices A, B, and D do not present with life-threatening conditions requiring emergency intervention. Choice A mentions symptoms of pleurisy, which may be painful but not immediately life-threatening. Choice B describes symptoms of bronchitis, which may require medical attention but not of an emergent nature. Choice D reflects a common complaint in asthma but does not suggest an immediate life-threatening situation unless severe respiratory distress is present.

Correct Answer: A

Rationale: The correct answer is peroneal nerve injury. The head of the proximal fibula is in close proximity to the peroneal nerve, making it susceptible to injury when there is a fracture. The peroneal nerve runs along the fibula and can be affected by trauma to this area. Choice B, tibial nerve injury, is incorrect as the fracture site is closer to the peroneal nerve, not the tibial nerve. Choice C, sciatic nerve injury, is incorrect as the injury is more localized to the fibular head area where the peroneal nerve is affected. Choice D, femoral nerve injury, is incorrect as the femoral nerve is not immediately adjacent to the proximal fibula and is not typically affected by this type of injury.

Correct Answer: D

Rationale: The correct answer is respiratory alkalosis. In respiratory alkalosis, there is an elevated pH and low carbon dioxide levels (PaCO2 < 35 mmHg). In the given arterial blood gas reading, the patient's pH is 7.41 (within normal range), PaCO2 is 29 mmHg (below normal range), indicating respiratory alkalosis. The bicarbonate level is normal (25 mEq/l), ruling out metabolic acidosis or alkalosis. The low PaO2 (54 mmHg) may indicate hypoxemia, but it is not directly related to the acid-base disorder being assessed. Metabolic acidosis (choice A) is characterized by low pH and low bicarbonate levels, which are not present in this case. Respiratory acidosis (choice B) is indicated by low pH and high PaCO2 levels, which also do not match the provided data. Metabolic alkalosis (choice C) is defined by high pH and high bicarbonate levels, which are not seen in this scenario.