The answer is: [D]:
___________________________________________________________
They are often used to combine choppy sentences.
______________________________________________________________
Conjunctions are often used to combine choppy sentences.
____________________________________________________________
Note: The questions asks about CONJUNCTIONS —NOT about "contractions".
____________________________________
Choice "A" is incorrect. They are not used to combine two or more LONG sentences. If sentences are already long, then do not need to be combined with a conjunction.
_____________________________________
Choice: "B" is incorrect. To the contrary, the use of conjunctions actually makes sentences longer.
________________________________________
Choice "C" is incorrect. To the contrary, the use of conjunctions should be used (appropriately, of course) in essays. The use of "contractions" should not be used in essays or formal writing.
________________________________________
Choice "D" is correct. They are often used to combine choppy sentences for better reading and engagement.
_______________________________________________________
Answer:
There are no dependent clauses
And is the coordinating conjunction
"It was almost December" is an independent clause
"Jonas was beginning to be frightened is an independent clause
There aren't any prepositional phrases
Compound sentence
It adds to the overall effect on the readers because it shows that Jonas is uncertain and makes the readers realize the correction that Jonas makes to make the sentence more reasonable.
Explanation: