Which of the following is an example of a derivational morpheme?
-
A
The '-s' added to 'cat' to form 'cats'
-
B
The '-ed' added to 'walk' to form 'walked'
-
C
The prefix 'un-' added to 'happy' to form 'unhappy'
-
D
The '-ing' added to 'run' to form 'running'