Which expression does NOT simplify to 1?

fg^3 / g^3f = 1
f^4 / f*f*f*f = f^4 / f^4 = 1
f^2g^3 / f^3g^2 = g/f
f*f/f^2 = f^2 / f^2 = 1
Answer:
f^2g^3 / f^3g^2