The prefix in- is changed to im- in improper, ir- in irreconcilable and il- in illegal, which shows that（ ）.

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

正确答案是C