Group 1: Spelling rule ‘kn’ ‘gn’

know, knock, knee, knitting, knife, gnat, gnaw, gnash, gnome, gnarled

Group 2:

Know Knock Knee knitting, knife

Group 3: spelling rule ‘ay’ ‘ou’

play, tray, clay, crayon, stay, cloud, found, loud, about, sound

Group 4: spelling rule ‘s’ ‘a’ ‘t’ ‘p’

sat, cat, pat, tap, cap