Group the words according to a particular type of morphemic distribution. MODEL: worked - bells - tells -fells - telling - spells - spelled - spelt -felled - bell. spells - spelled: the allomorphs "-s" and "-ed" are in contrastive distribution (= fells - felled); bell - bells: the allomorph "-s" and the zero allomorph are in contrastive distribution; spelt - spelled: the allomorphs "-t" and "-ed" are in non-contrastive distribution; worked-spelled: the allomorphs "-ed" [t] and "-ed" [d] are in complementary distribution, etc. a) burning - burns - burned - burnt; b) dig - digs - digging - digged - dug - digger;

a) burning - burns: the allomorphs "-ing" and "-s" are in contrastive distribution; burned - burnt: the allomorphs "-ed" and "-t" are in non-contrastive distribution;

b) dig - digs: the allomorphs "-s" and zero allomorph are in contrastive distribution; digging - digged: the allomorphs "-ing" and "-ed" are in complementary distribution; dug - digger: the allomorphs "-ed" and "-er" are in contrastive distribution.