suppose the following 5'-->3' dna sequence was mutated from gagagagagagagagaac to gagacagagagagagaac.

i believe the answer is snake.

on island x the species needed to adapt because they were being subject to predators which didn't inhabit island y.  

the last one: artificial selection/genetic engineering

plant breeding is modifying the genetic composition of the plant - but this isn't cloning (which is specifically introducing a gene into a genome). but you are artificially selecting for the phenotype that you want.

the second one is literally genetic engineering - the gene would have been cloned first and then inserted or genetically engineered into the new plant cell (the cotton).