Correct Answer: B

Rationale: The correct answer is B: Fever and abdominal pain. In children, appendicitis commonly presents with fever and abdominal pain. The pain typically begins around the umbilicus and then moves to the lower right quadrant. Choices A, C, and D are incorrect because vomiting and diarrhea, rash and joint pain, and difficulty breathing are not typical symptoms of appendicitis in children.

Correct Answer: B

Rationale: In laryngotracheobronchitis (croup), a child may become restless due to poor oxygenation. Increasing the oxygen concentration in the oxygen tent is crucial to improve oxygenation levels and manage symptoms effectively. Restraint is not appropriate in this situation, as it may cause distress and worsen the child's condition. Taking the child to the playroom is not indicated when the child requires oxygen therapy. While comforting the child is important, the priority in this scenario is to optimize oxygen delivery to improve respiratory distress.

Correct Answer: C

Rationale: Assisting parents of a SIDS infant in coping involves alleviating feelings of guilt and blame, providing emotional support, and offering appropriate counseling. It is crucial to address the parents' emotional well-being and help them cope with the loss. Choice A is not the best answer as it focuses solely on grief counseling, while the primary concern is addressing feelings of guilt and blame. Choice B is inappropriate as remaining detached does not provide the necessary emotional support these parents need. Choice D is incorrect as discussing the parents' mistakes can intensify their feelings of guilt and blame, rather than helping them cope effectively.

Correct Answer: B

Rationale: Limited abduction of the hip is a common sign of developmental dysplasia of the hip in infants. It indicates possible hip dislocation or instability, making it a key clinical manifestation to assess for DDH. Dislocated patella (Choice A) is not typically associated with DDH. Swelling of the knee (Choice C) and hyperextension of the leg (Choice D) are not specific signs linked to DDH in infants, further supporting why they are incorrect choices.

Correct Answer: D

Rationale: The correct answer is D. A placebo serves as a control for comparison with the treatment group, helping to eliminate bias and ensure the results are due to the treatment itself. Placebos are crucial in research to distinguish the actual effect of the treatment from psychological or subjective factors. Choice A is incorrect because the purpose of a placebo is not related to reducing the cost of the experiment. Choice B is incorrect because while placebos are used in double-blind studies, their primary purpose is not to make the experiment double-blind. Choice C is incorrect because the purpose of a placebo is not to increase the number of participants but rather to serve as a comparison group for the treatment being tested.