STUDENT'S ASSIGNMENT:
M- mango ,motor, morning
N- noon, north, never
O- open, oil, oven

TEACHER'S CORRECTION:
M- mango ,motor, monkey
N- needle, north, necklace
O- owl, oil, oven
 
TEACHER'S EXPLANATION:
Even though those words that  you used are all starting in that letter's, but they are not "things".
> morning - (noun) - it is a period  of a day
> noon - (noun) - it is a period  of a day
> never - it is an adverb and not a thing

TEACHER'S NOTE:
Hello Doris! We are now in the  letters M, N and O. Continue to practice your pronunciation on those letters. I am happy that you do your assignment  today. Thank  You so much!