An air bubble in a tank of water is rising with terminal (constant) velocity. The forces acting on the bubble are 
, 
and 
, as shown.
The upthrust on the bubble is . Which statement about the forces is correct?
is the viscous force on the bubble, is the weight of the bubble and 
.
is the viscous force on the bubble, is the weight of the bubble and 
.
is the weight of the bubble, is the viscous force on the bubble and .
is the weight of the bubble, is the viscous force on the bubble and .
