What did Mendel's cross-pollination of pea plants prove?

A)Inherited factors combine in offspring to create entirely new characteristics.

B)There is no such thing as a true-breeding plant; they all have hidden factors.

C)It takes four generations of offspring to identify the parents' factors.

D)Each parent only passes on one-half of its hereditary factors to each offspring.

Please help!!

D) Each parent only passes on one-half of its hereditary factors to each offspring.

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).