Initially a Child with a Ventricular Septal Defect (VSD)and Pulmonic

Initially a child with a ventricular septal defect (VSD) and pulmonic valve stenosis is acyanotic.Over time,however,the pulmonic valve stenosis worsens and the child becomes cyanotic.What is the most probable explanation?

A) The child becomes severely anemic and hypoxemic.
B) The pulmonic stenosis elevates right ventricular pressure, thereby shunting unoxygenated blood from the right ventricle into the left ventricle; unoxygenated blood is then pumped to the systemic circulation.
C) Blood is shunted from the left ventricle into the right ventricle.
D) Excess blood in the right ventricle and pulmonary artery fills the alveoli, thereby causing hypoxemia and cyanosis.