Why does the reactivity of metals increase from right to left on the periodic table?

The correct answer is C. Metals on the right have more protons, causing valence electrons to be held more strongly.

Here's the reasoning:

As you move from right to left across a period in the periodic table, the number of protons in the nucleus of the element decreases. Metals on the right side of the periodic table (like transition metals) typically have more protons and thus attract their valence electrons more strongly. This means that it becomes more difficult for these metals to lose their valence electrons compared to metals on the left side of the table (like alkali metals), which have fewer protons and therefore hold their valence electrons less tightly. As a result, the reactivity of metals increases from right to left because it is easier for those on the left to lose their valence electrons and react with other elements.