Correct answer only ! i cannot retake how is the underlined prepositional phrase in this sentence being used?

Which group or words is not a phrase? a.) leaving behind the dog b.) because she smiled at me c.) smashing into a fence d.) before the first test e.) pushing the sofa

The greatest gift the sumerians gave the world was the invention of writing. the sumerians were a wealthy people. they needed some way to keep track of what they owned. they began drawing pictures. they used a reed as a pen. they drew on soft pieces of clay. the soft clay was then dried in the sun. the tablet became a permanent record. later, the sumerian drawings changed into wedge-shaped symbols. this kind of writing is called cuneiform. by putting symbols together, the sumerians could write entire sentences.

Which two parts of this excerpt from authur conan doyle's " the contest " show policies lack of knowledge about the rules and restrictions of his society