Complete the following sentences :
(a) Two balls, one of iron and the other of aluminium experience the same upthrust when dipped completely in water if
(b) An empty tin container with its mouth closed has an average density equal to that of a liquid. The container is taken 2 m below the surface of that liquid and is left there. Then the container will
(c) A piece of wood is held under water. The upthrust on it will be