What evidence supports land at one point being covered by ocean

The answer is; the presence of diatomaceous earth in the soil.

This means that diatoms existed in the region. Diatoms are silicified microalgae that exist in oceans, brackish waters, even in freshwaters. They divide vegetatively and in large numbers. When they die, they fall off (precipiate) to the ocean beds and accumulate with sediment to form diatomaceous earth over time.

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).