Botanist: On the remote island of Tropica, it is known that early sett

Hi,
lets see the choices..

B. The wild sunflower plants on the island of Tropica today are more similar to the original variety than today’s farmed plants.
lets take the same premise etc as written by you..
Premise- the wild plants have not been selectively cultivated over the years as the farmed plants have
Assumption- The wild sunflower plants on the island of Tropica today are more similar to the original variety than today’s farmed plants..
Conclusion- By studying today’s wild sunflower plants on the island of Tropica, we can learn much more about that original variety of sunflower

now we know from the para that "the wild plants have not been selectively cultivated over the years as the farmed plants have." And conclulsion is derived that "By studying today’s wild sunflower plants on the island of Tropica, we can learn much more about that original variety of sunflower."
here we are not told if the selective cultivation has had any effect on farmed variety so as to prefer wild over it, or after such a long time hasn't the change in environment brought certain changes in wild plants too..
But since the author is concluding that wild should be preferred over farmed, he believes/assumes that The wild sunflower plants on the island of Tropica today are more similar to the original variety than today’s farmed plants..
clearly the assumption here to prefer wild over farmed sunflower..

D. The selective cultivation of farmed plants over the past 10,000 years has led to few if any significant changes from the original variety.
This tells us that there could be very few significant changes and possibly no changes in farmed crop..
This assumption would go against not studying the farmed crop, after all they too have undergone very few changes, which too may not be true..
so no reason to prefer wild over farmed, or to completely neglect farmed crop

hope it helps