Final answer:
The child's presentation of a fixed and widely split S2, along with a soft ejection murmur, suggests an Atrial Septal Defect (ASD) as the most likely diagnosis among the provided options (D). Other severe conditions, such as Tetralogy of Fallot, would present with additional symptoms like cyanosis, which are not observed in this case.
Step-by-step explanation:
A five year old child was noted to have a loud S1 and a fixed and widely split S2 that does not vary with respiration, along with a soft, mid-systolic ejection murmur heard best on the left in the second intercostal space. These symptoms are indicative of a congenital heart defect. Among the options given, the most likely diagnosis for these findings is an Atrial Septal Defect (ASD). This diagnosis is supported by the presence of a widely split S2 and an ejection murmur without additional signs of heart failure such as nail clubbing, hepatomegaly, or jugular venous distension.
Septal defects are not uncommon and may be first detected through auscultation using a stethoscope. These defects involve an abnormal opening in the heart septum that separates the cardiac chambers, allowing blood to flow between them. Among the conditions listed, ASD typically presents with a fixed split S2 and may be associated with an ejection murmur due to increased flow through the pulmonary valve. Given that this child is healthy and active without cyanosis or signs of heart failure, conditions like Tetralogy of Fallot, which would typically show more severe symptoms and signs of cyanosis, are less likely.