According to the positions which affixes occupy in words, affixa

According to the positions which affixes occupy in words, affixation falls into two subclasses: prefixation and ( ).
【正确答案】：SUFFIXATION
【题目解析】：根据词缀在词中的位置，词缀法又可分为前缀法和后缀法。答案为suffixation。