Questions: Mark Twain's novel The Adventures of Huckleberry Finn shows the worst and the best qualities of American society explores Huck's moral struggle over helping Jim to escape and introduces Americans to a new, colloquial way of writing.

The answer is: Mark Twain's novel The Adventures of Huckleberry Finn shows the worst and the best qualities of American society, explores Huck's moral struggle over helping Jim to escape, and introduces Americans to a new, colloquial way of writing.

This clause is an independent clause and should be followed by a comma to separate it from the next independent clause.

This clause is another independent clause and should be followed by a comma to separate it from the next independent clause.

This clause is the final independent clause in the series and does not need a comma before it because it is preceded by the conjunction "and."

By adding commas after "society" and "escape," the sentence is correctly punctuated to separate the independent clauses.