On is the only preposition in this sentence. A preposition shows location, such as, on, over, beside, etc.
Answer:
An objective tone means the author of the essay is not sharing her/his personal opinion, bias or judgment about a subject, but presenting the information impartially.
Sentence B is the correct option. When using "however" to write a compound sentence, we should write a semi-colon before and a comma after it. When "however" is used at the beginning of a sentence, we should write a comma following it.