Identify the sentence(s) punctuated correctly.

The correct answer is Option D (We have, of course, to learn by experience.).

Key Points:
• This question evaluates the candidate's understanding of English punctuation rules, a crucial grammatical concept frequently tested in MPSC and other competitive examinations. Grasping the correct usage of commas and parenthetical elements is essential for mastering English language mechanics.
• Option 4 is the correct answer according to the official MPSC answer key. The underlying rule states that parenthetical expressions or interrupting phrases, such as 'of course', must be enclosed within commas to separate them from the main clause.
• Let us analyze why the other options are grammatically flawed. Option 1 is incorrect because it misses a preceding comma before the interrupter 'unfortunately'. Option 2 places an unnecessary and disruptive comma after 'Come', breaking the verb phrase. Option 3 is actually punctuated correctly with a semicolon, but according to the MPSC official final key, Option 4 is deemed the intended correct answer for illustrating the parenthetical comma rule.
• A common MPSC trap is presenting sentences missing one out of two required parenthetical commas.
• Consistent practice of punctuation rules ensures higher accuracy and prevents unnecessary loss of marks in the examination.
• Key Takeaway: Remember: Parenthetical or interrupting expressions must be enclosed by commas on both sides.