What caused the chromosomal alteration in number 21?

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).

a. an idea which cannot be disproven!

explanation:

answer; the code in musculoskeletal system subsection is associated with deep tissue possibly to the bone;