Artifacts are useful and millennium is helpful.
The appropriate language that should be used in a letter of complain is formal language. The tone used in the letter should be positive, courteous and straight to the point. Word choice is very important, choose your words carefully to convey your feelings. Be objective in your writing and use active constructions in your sentences.
Dank
Mocking
The situation in the first sentence leads to the description of that area that is very dank. In the second sentence a person laughing because of the lights would imply that they are being mocked.
A clause is C, a group of words that contains both a subject and predicate (verb).
The correct answer is D. Beyond the horizon.
This is because phrases don't have verbs in them and this is the only option that doesn't have a verb in it.