The prefix in- is changed to im- in improper, ir- in irreconcila

The prefix in- is changed to im- in improper, ir- in irreconcilable and il- in illegal, which shows that（ ）.
A、morphemes are abstract units
B、morphs are actual spoken, minimal carriers of meaning
C、allomorphs are phonetically conditioned and thus predictable
D、affixes can be added to other morphemes to create new words
【正确答案】：C
【题目解析】：本题考查前缀法。前缀in-在improper（不合适的）中被改为im-; 还有irreconcilable（不能调和的）中的ir；以及illegal（不合法的）中的il，这个例子表明了同构词在语音上是有条件的，因此是可预测的。故选C。A选项意思为语素是抽象单位；B选项意思为变形词是实际的口语，最小的意义载体；D选项意思为词缀可以添加到其他语素中来创造新词。均不符合题意。