Final answer:
The most common type of ventricular septal defect is B. Membranous, which occurs in the interventricular septum that separates the left and right ventricles.
Step-by-step explanation:
Most Common Type of Ventricular Septal Defect
The most common type of ventricular septal defect is B. Membranous. A ventricular septal defect is an abnormal opening in the interventricular septum, the wall that separates the left and right ventricles of the heart. The membranous portion is the upper part of the interventricular septum and is located below the aortic valve. This area is the most likely location for a defect due to its complex structure and the amount of blood flow it receives.
In contrast, the other septums in the heart, such as the atrioventricular septum and the interatrial septum, have different roles. The atrioventricular septum separates the atria from the ventricles and contains openings for the atrioventricular valves which include the tricuspid and the bicuspid valves. Meanwhile, the interatrial septum separates the left and right atria and normally hosts the foramen ovale during fetal development, which usually closes after birth.
The functional significance of the interventricular septum is exemplified by the need for it to be intact to maintain separate pulmonary and systemic circulations within the heart.