The activation of Β2 receptors in the bronchi causes bronchodilation (an increase in diameter of the bronchi), making it easier to breathe. Which of the following neurotransmitters would be useful for a person suffering from an episode of bronchoconstriction (a reduction in the diameter of the bronchi)?epinephrine
eiphones

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).