A patient is admitted to the hospital for heart surgery to have a Tetralogy of Fallot repair. The parents are asking the nurse to explain one of the underlying causes of their child's cyanosis. Nurse Lisa is correct in her explanation when she says:

The underlying cause of cyanosis in Tetralogy of Fallot is aortic stenosis.

The underlying cause of cyanosis in Tetralogy of Fallot is a patent ductus arteriosus (PDA).

The underlying cause of cyanosis in Tetralogy of Fallot is mitral valve regurgitation.

The underlying cause of cyanosis in Tetralogy of Fallot is a ventricular septal defect (VSD).