An object is descending through a viscous liquid at a steady speed. $F_u$ represents the upthrust acting on the object because of the liquid. $W_L$ represents the weight of the liquid displaced by the object. $W_o$ represents the weight of the object. Which equation must be true?
- A$F_u = W_L$
- B$F_u = W_o - W_L$
- C$F_u = W_o$
- D$F_u = W_o + W_L$