What is a preposition?

What is the preposition in this sentence?
"Sally read her book in the living room."

her

tell me the answer to what is the preposition in this sentence sally read her book

and give me a thumbs up please

kk out peace

Sally has been reading that book ______ she arrived

Tell me the answer of this preposition

The correct answer is in look it up

for

http://www.chompchomp.com/terms/preposition.htm