(a) (i) & (ii)
Reason — Characteristic properties of upthrust :
- Larger the volume of a body submerged in a fluid, greater is the upthrust.
- For the same volume of a body inside a fluid, more the density of fluid, greater is the upthrust.
- The upthrust acts on the body in upward direction at the centre of buoyancy i.e., the centre of gravity of the displaced fluid.