Which of the following DNA mutations is likely to have the most negative effect on the protein it specifies? A codon deletion at the end of a sequence
A base pair deletion resulting in a different amino acid
A substitution for one serine codon for a different serine codon
A substitution for one stop codon for another stop codon

black

lasagna

lunch

math

the answer is c because it is most logical.

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).