Which congenital heart disease causes cyanosis when not repaired? (select all that apply)

A. Pulmonary atresia leads to little or no blood flow to the lungs, resulting in severe cyanosis if not surgically repaired. B. PDA typically causes a left-to-right shunt and does not usually result in cyanosis unless other defects are present. C. Transposition of the great arteries (TGA) creates parallel circulations, leading to severe cyanosis without mixing of blood. D. Tetralogy of Fallot is a classic cyanotic heart defect, especially during "tet spells" due to right-to-left shunting.