Mark Twain's books are definitely in the "must read" category for students.
Which revision of this sentence changes the tone to a more formal one? (4 points)
If you haven't read Mark Twain, you haven't studied literature.
Mark Twain is awesome, and everyone should read his works.
Reading Mark Twain is better than eating gourmet chocolates by a pool.
The works of Mark Twain should be required reading for all students.