What must usually happen in order for a dead organism to be preserved as a fossil?

What is the empirical formula for c4h8o2

Mercury turns to vapor at 629.88 k how much heat is lost 175 g of mercury vapor at 650 current condenses to a liquid at 297 ca mercury turns to weber at 629.88 kelvin how much he is lost 175 g of mercury vapor and 650 coming condensers to liquidate 297 kevin

Which is an example of a reversible physical change?