What does the symbolupper deltain a chemical equation mean?

Which statement describes the phase change that occurs when dry ice is placed in an open container at room temperature?

The molecular weight of carbon dioxide, co2, is 44.00 amu, and the molecular weight of nitrous dioxide, no2, is 46.01 amu, so no2 diffuses co2

Need , hurry pls create a superhero out of the element iron, what are its powers and his sidekick ( an element that works well with iron). how was the superhero made and who discovered him