However, there some exceptions: Some nouns end in ‘-f’ but their plurals are only formed by adding ‘-s’ only.
Belief – Believes
Roof – Roofs
Proof – Proofs
Students' Task
Allow
the students to make a list of the words that end in ‘-f’ and ‘-fe’, and allow
them to form the plural forms from the list they have made. Pass through as
they work to help them.
At
the end, correct their mistakes if there are any and conduct pronunciation
drills of the words they have listed. As they produce more examples, students should be aware of the exceptions concerning this rule.