B: A political cartoon uses sarcasm to poke fun at the latest policy change in government.
The complete prepositional phrase in the sentence stated above is "in the door's key hole". As the name suggests, this type of phrase is introduced by prepositions which in this case is with the use of preposition "in". It answers the question "where" which refers to the location of the object it modifies.
Most important in astronomical history--the one whose orbit has been.