The correct answer is A) Heated sea water is injected into a vacuum chamber. In a flash type evaporator, sea water is heated and then injected into a vacuum chamber. The reduced pressure in the chamber causes the sea water to "flash" or rapidly boil, producing fresh water vapor. This vapor is then condensed and collected as distilled water, leaving behind the salts and minerals from the original sea water. The key operating principle is the use of a vacuum to lower the boiling point of the sea water, allowing distillation at a lower temperature compared to normal boiling. The other options are incorrect because they do not accurately describe the flash evaporation process. Option B refers to atmospheric boiling, option C describes a different evaporation method, and option D involves an eductor which is not a core component of a flash evaporator.