Answer:
A. a strictly formal, argumentative tone
D. unpleasant remarks about a teacher
E. simple sentence constructions
Step-by-step explanation:
You definitely want to avoid D because you could absolutely get in trouble with them.
You completely want to avoid A because those who are listening to you will become bored and when speaking, this isn't a lecture/ debate contest, it's graduating speech. You're freaking graduating and you shouldn't argue about that.
For E, I don't know what to say to that, but just... avoid it.