Point out the correct sentences.
a. Will you convey my apologies to your grandparents.
b. Is it bad to be hostile to the persons who help us !
c. Pointing to others for our own mistakes is a dangerous habit, isn't it?
d. For years he has been listening to the advertisement "Tobacco chewing is injurious to health', and still he continues to chew it.
Answer options:

The correct answer is Option D (None of these).

Key Points:
• Sentence a: 'Will you convey my apologies to your grandparents.' is an interrogative sentence/polite request requiring a question mark (?), but ends with a period (.).
• Sentence b: 'Is it bad to be hostile to the persons who help us !' is an interrogative question requiring a question mark (?), but erroneously ends with an exclamation mark (!).
• Sentence c: The correct idiom is 'pointing the finger at others' or 'blaming others for', not 'pointing to others for'.
• Sentence d: It has mismatched quotation marks (opens with double quotes " and closes with a single quote ') and improper syntax.
• Option 4 (None of these).
• Because all four sentences have punctuation or grammatical defects, none of the sentences are fully correct.
• Key Takeaway: Due to missing/erroneous punctuation and mismatched quotation marks, none of the given sentences are correct.