On Wednesday, August 15, 1934, William Beebe and Otis Barton made history by descending in the Bathysphere-basically a steel sphere 4.75 ft in diameter- 3028 ft below the surface of the ocean, deeper than anyone had been before.

(a) As the Bathysphere was lowered, was the buoyant force exerted on it at a depth of 10 ft greater than, less than, or equal to the buoyant force exerted on it at a depth of 50 ft?

(b) Choose the best explanation from among the following:

I. The buoyant force depends on the density of the water, which is essentially the same at 10 ft and 50 ft.

II. The pressure increases with depth, and this increases the buoyant force.

III. The buoyant force decreases as an object sinks below the surface of the water?