D. The valence electrons of the larger atoms are farther from the nucleus and are easier to remove, so the metals near the bottom are more reactive than those at the top.
Explanation:
Option D is the correct answer because when we move down the group the sizes of the atoms increases, as a result of that, the valence electrons are far from the nucleus. This will make it easier for the valence electrons to be removed because the force of attraction between the nucleus and the valence electron decreases; so they are less tightly bound.
Therefore, the metals near the bottom are more reactive than those at the top i.e reactivity increases as you go down the group.
