Botanist: In an experiment, scientists raised domesticated radishes in a field with wild radishes, which are considered weeds. Within several generations, the wild radishes began to show the same flower color as the domesticated ones. This suggests that resistance to pesticides, which is often a genetically engineered trait, would also be passed from domesticated crop plants to their relatives that are considered weeds. Which one of the following, if true, most strengthens the botanist's argument? ['It is more difficult for flower color to be transferred between domesticated and wild radishes than it is for almost any other trait to be passed between any two similarly related plant species.', 'When the ratio of domesticated radishes to wild radishes in the field increased, the speed with which the flower color passed to the wild radishes also increased.', 'Radishes are not representative of crop plants in general with respect to the ease with which various traits are passed among members of closely related species.', 'It is much easier in principle for genetic traits to be passed from wild plants to their domesticated relatives than it is for such traits to be passed from the domesticated plant to the wild relative.']