就原理而言，磨齿加工方法通常分为（ ）磨齿和（ ）磨齿两大类。In principle , the gear grinding methods are usually divided into ( ) and ( ) .

A、蜗杆砂轮磨齿 grinding with
worm abrasion
wheel ;
B、成形砂轮磨齿 forming grinding
method;
C、碟形砂轮磨齿
grinding with dish
abrasion wheel;
D、范成法磨齿 generating grinding method