Emily collects and trades rocks. She starts with 8x2 rocks, for some number x, and then buys 7x4. She then trades away x5, then gives away 9x, and finally sells another 5 rocks. Write an expression for the number of rocks Emily now has in standard form. A. −9x + 8x2 + 7x4 − 5 − x5 B. 8x2 − 5 + 7x4 − 9x − x5 C. −x5 + 7x4 + 8x2 − 9x − 5 D. −5 − 9x + 8x2 + 7x4 − x5