I would like to inform you that your product is faulty. Put simply, it doesn't properly work.

If you wished to maintain a formal tone in this message, which choice would make the best next sentence?
A) This has caused great inconvenience.
B) You won't believe how angry I am!
C) I don't want to hear about how this just a simple mistake, either.
D) I've followed the directions, but still get nothing but a big headache.

"Formal" means polite... in a grown up way....

only A) is polite in a grown up way : )

Um what is this

If you wished to maintain a formal tone in this message, the best next sentence would be:

A) This has caused great inconvenience.