Which of the following characteristics of these offspring confirms that they were produced by sexual reproduction?

sexual reproduction produces offspring with novel combinations of genes. species that reproduce sexually must maintain two different types of individuals, males and females, which can limit the ability to colonize new habitats as both sexes must be present.

meiosis is the first to occur after the nuclei of opposite of opposite mating types fuse

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).