Genitive case involves adding an apostrophe followed by "s" to the end of noun.
Correct answer: option (A)
Reason:
- Apostrophe is in correct place. (Paul's grandad= grandad of Paul ; month's winner= winner of the month)
- Punctuation (comma) is in correct place.
Option (B) (C) (D) are incorrect.
Reason:
For option (B) - Punctuation (comma) is absent at required position. (Between words: man and Paul's ; Between words: grandad and is)
For option (C) - Apostrophe is absent before s in 'months'
For option (D) - Apostrophe is absent before s in 'Pauls'
Final answer; That tall man, Paul's grandad, is this month's winner.