Which word is the preposition and which word is the object of the preposition in this sentence? 
 A great big moth flew through the open window.
 A.
 preposition: a; object of the preposition: moth
 B.
 preposition: through; object of the preposition: window
 C.
 preposition: great; object of the preposition: big
 D.
 preposition: flew; object of the preposition: through