If a quantity y varies as the sum of three quantities of which the first varies as x, the second varies as — x + x2 , the third varies as x3 — x2 , then what is y equal to?

• A. kx3, where k is a constant
• B. kx, where k is a constant
• C. kx + lx2 + mx3, where k, 1, m are constants
• D. kx2, where k is a constant