You are studying two new species that have a mutualistic relationship. How would you determine if the mutualism is a facultative or obligate mutualism?

of those who start drinking before they're 15 will develop alcohol dependence

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).