The oldest and hardest cow beef may be made as tender and tasty as young and choice met. "This declaration was made by the French physicist Denis Papin in book published in 1681, which described his "New Digester" or pressure cooker.  It was a cast iron pot with an air-tight lid, which allowed liquids to boil at a higher temperature than usual, and so it cooked food in a quarter of the time.  The food was cooked by pressurized steam being forced through it at about 121degC.  All pressure cookers were made of cast iron until 1905,  when the first aluminum model was made in America. In 1938, Alfred Vischer, a man from Chicago, U. S. A., designed a simple interlocking pan and lid, and an improved pressure-tight seal --a replaceable rubber sealing ring. When Vischer's patent expired in 1954,  many companies entered the field,  and the rapid pressure cooker became popular with people with people who had little time to cook or had to supply food for unexpected guests. In the writer's opinion, the best advantage of a pressure cooker is that  _  .
the oldest and hardest cow beef can be made tender and tasty it allows liquids to boil at a higher temperature than usual it can help people to supply food for unexpected guests it helps people to spend much less time in cooking