The stem has more things to transport that's why it has more vascular bundles. The roots only get water from the ground and moving nutrients from the soil to transfer it to the stem. Having more vascular bundles helps the stems to transfer things to leaves and other parts of the plants.
The answer is a because you're not focusing on numbers (quantities), you're simply observing something
I think this is the answer key.. tell if you need help read it :)
Vestigial traits are adaptations to environmental pressures which are no longer present.
homologous structures are similar structures found in different species that were present in a common ancestor.
analogous traits are similar traits found in different species that were developed independently (this process is known as convergent evolution)
I think the answer would be "A"