<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 2-year-old boy is brought to the physician because of coughing and difficulty breathing that started shortly after his mother found him in the living room playing with his older brothers toys. He appears anxious. Respirations are 33min and pulse oximetry on room air shows an oxygen saturation of 88. Physical examination shows nasal flaring and intercostal retractions. Auscultation of the lungs shows a high-pitched inspiratory wheeze and absent breath sounds on the right side. There is no improvement in his oxygen saturation after applying a non-rebreather mask with 100 FiO2. Which of the following terms best describes the most likely underlying mechanism of the right lungs impaired ventilation?? A: Alveolar hyperventilation, B: Alveolar dead space, C: Diffusion limitation, D: Alveolar hypoventilation, E: Right-to-left shunt,  <response>: Based on the information provided in the question stem, this 2-year-old boy is showing signs of respiratory distress including coughing, difficulty breathing, nasal flaring, intercostal retractions, and hypoxemia low oxygen saturation. The wheezing indicates bronchoconstriction, while the absent breath sounds on the right side point to a problem with ventilation of the right lung. The lack of improvement with 100 oxygen suggests a shunting process where unoxygenated blood is bypassing the lungs and entering the systemic circulation without being oxygenated. Of the choices provided, a right-to-left shunt best explains these findings.E: Right-to-left shunt 