The word, 'Mr.' is an abbreviation of the word, 'Mister' and is used as a title for men. The letters, 'Mr' are to be followed by a dot.
'Sharma' and 'Nandini' are proper nouns denoting names of people. The first letters of these words, i.e 's' and 'n' have to be capitalised.
The given sentence is an assertive sentence. Hence, it has to end with a full stop.
The words 'his wife' and 'Nandini' refer to the same person. A comma is used in between two such nouns (They are called nouns, in apposition). The correct way of writing is: His wife, Nandini.
Option A is incorrect as the first letters of the proper names 'Sharma' and 'Nandini' are not capitalised. There is no comma between the words, 'his wife' and 'Nandini.
Option B is incorrect as the first letter of the proper name 'Nandini' is not capitalised. There is no comma between the words, 'his wife' and 'Nandini.
Option D is incorrect as the word 'Mr' is not followed by a dot. The first letter of the proper name 'Nandini' is not capitalised. There is no comma between the words, 'his wife' and 'Nandini'. An exclamatory mark at the end of an assertive sentence is grammatically incorrect. Given these errors, this option is incorrect.
Option C is correct as all the above punctuation rules are followed.