Which of these words is NOT a preposition?

a. throughout

b. going

c. beneath

d. among

The answer is B, going. Prepositions are words that give information to the reader. This information can include where something takes place (such as 'at' the mall), when or why something takes place (such as 'before' lunch), or general descriptive information (such as the girl 'with' the cute tattoo). Going is the only word here that cannot answer these questions of where, when or why. It is a verb.