Which statement below is correct about the form -er in the words listed here: teach er , bigg er , eras er , London er ?
A.
All these words have the same morpheme.
B.
Every word listed in this question has an allomorph of {-er}.
C.
Some different morphemes can be represented by the identical form.
D.
-er here is used to form new words, hence a derivational affix.