Why was ice used during the extracting dna

The Cold Water  temperature helps increase the attachment of the DNA Explanation:

Using ice-cold ethanol and ice-cold water increases the yield of DNA. Low temperatures protect the DNA by slowing down the activity of enzymes that could break it apart. ... DNases in the cytoplasm would destroy the DNA of viruses entering the cell. Cold ethanol helps the DNA to precipitate more quickly

answer:

sequence 1- deletion

                  2- duplication

                  3- insertion

                  4- substitute

                  5- inversion

if your own plato the answer is b. the fern transitioned from sporophyte generation to gametophyte generation.