The mood of this paragraph is so moody-no pun intended- so dark and mysterious. It almost makes you engrossed into this character's feelings. You feel that bottomless pit in his stomach, you almost hear his hear beating out of his chest. Everything in this gives you almost a hurried pace to it, almost like that feeling you get in the movies when something spectacular is happening but everything is completely silent-not one character talking-only your own interpretation of their thoughts-their feelings.
It would be C. Informal because you are suppose to start business letters with Dear (Yourname) and it's the only one that does.
"poetic description" is the only real option from the list that is not common in expository writing, although careful descriptions can indeed be used as long as the point remains clear and forceful.
It’s very good the ether person is correct
