<span>"Ha! Would a madman have been so wise as this?"</span>
The difference between an autobiography and a biography, is an autobiography is what a person, writes about themselves, and a biography is when someone studies about a subject and writes about it.
Hope this helps!
c. One must wear one's identity card at all times when at work
Using the pronoun "you" makes it less formal. Since c doesn't use "you" it's the most formal.