How has increased global travel boosted the spread of certain species?

Explanation:

Many pathogenic species of bacteria, virus, and other microbes are more prevalent in developing or tropical countries rather than in developed countries.

When an individual’s immune system is weak they become more susceptible to get infected and become carriers of that particular species.

The species grows, develops, and multiplies in the host’s body and when the traveler travels to his/her home country or any other place he/she can transmit the disease to others and again the species grows in numbers. Higher the rate of spread of infection higher is the increase in species.

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).

to this one it would be receptive field