Deep-sea organisms live under conditions of very high external pressure. Answer the following questions related to the variation of pressure with depth in a fluid.
(i) Explain qualitatively why the pressure experienced by an object increases as it is taken to greater depths under water.
(ii) Distinguish between gauge pressure and absolute pressure, illustrating your answer with one example of each from everyday situations.
(iii) High-density liquids such as mercury are preferred over water in barometers. Give two reasons, based on the relationship between pressure and the height of a liquid column, to justify this choice.