Correct Answer: A

Rationale: Petechiae, infection, and fatigue are common signs and symptoms of leukemia related to bone marrow involvement. Petechiae are small red or purple spots on the skin caused by bleeding under the skin due to low platelet counts. Infection susceptibility increases due to decreased white blood cells from compromised bone marrow function. Fatigue is a common symptom of anemia resulting from decreased red blood cell production. Choices B, C, and D are incorrect as they do not align with the typical signs and symptoms of leukemia associated with bone marrow dysfunction.

Correct Answer: C

Rationale: Visible peristalsis and weight loss are classic clinical manifestations of pyloric stenosis. Visible peristalsis refers to the wave-like movements in the abdomen caused by the stomach trying to empty into the intestines due to the obstruction at the pylorus. Weight loss is often seen due to inadequate feeding and vomiting associated with this condition. Choices A, B, and D are not typical of pyloric stenosis. Abdominal rigidity and pain on palpation are more indicative of conditions like peritonitis. A rounded abdomen and hypoactive bowel sounds are more suggestive of conditions like constipation or bowel obstruction. Distention of the lower abdomen and constipation are not specific to pyloric stenosis and may be seen in various gastrointestinal issues.

Correct Answer: D

Rationale: A common clinical manifestation of bacterial meningitis is a positive Kernig sign, which indicates meningeal irritation. Kernig sign is elicited when the leg is bent at the hip and knee at 90-degree angles, and pain and resistance are felt with extension at the knee due to inflamed meninges. Options A, B, and C are not typically associated with bacterial meningitis. A rash is more commonly seen in viral illnesses, photophobia can be present but is not specific to bacterial meningitis, and jaundice is not a typical clinical manifestation of this condition.

Correct Answer: A

Rationale: The nurse should suspect measles based on the symptoms described, including the presence of Koplik spots (small, red spots with blue-white centers in the mouth). Measles typically presents with fever, irritability, runny nose, and a rash that begins on the face and spreads downward. Chickenpox (choice B) presents with vesicular lesions in different stages of healing and usually starts on the trunk. Fifth disease (choice C) presents with a 'slapped cheek' rash on the face and can cause joint pain. Scarlet fever (choice D) is characterized by a sandpaper-like rash, fever, and strawberry tongue.

Correct Answer: B

Rationale: The sweat chloride test is the gold standard diagnostic test for cystic fibrosis as it measures the concentration of chloride in sweat. In cystic fibrosis, there is an abnormal transport of chloride across epithelial membranes, leading to elevated sweat chloride levels. A chest X-ray may show characteristic changes in the lungs associated with cystic fibrosis, but it is not a definitive diagnostic test. Pulmonary function tests assess lung function but do not specifically diagnose cystic fibrosis. Sputum culture may identify respiratory infections but does not confirm the diagnosis of cystic fibrosis.