Three forces, A, B, and C, are acting on the same object with magnitudes a, b, and c, respectively. Force A acts to the right, force B acts to the left, and force C acts downward. What is a necessary condition for the object to move straight down? A. The magnitude of force A must be greater than the magnitude of force C, so A > C.

B. The magnitude of force A must be greater than the magnitude of force B, so a > b.

C. The magnitude of force A must be equal to the magnitude of force B, so a = b.

D. The magnitude of force C must be greater than the magnitude of forces A or B, so A < C > B.