True statement regarding Glucose $6$ phosphate dehydrogenase $($G$6$PD$)$ deficiency is $4$a$.$Hemolysis is always intravascularb.Younger red cells contain lower level of the enzyme than older onesc.Doesnt cause hemolysis in the first $4-6$ months of lifed.Mediterranean variant is associated with more severe diseasee.Ingestion of fava beans is the most common cause of hemolysis