Answer:
A.) S
Step-by-step explanation:
Anions form when elements have more electrons than protons. Some elements want to gain electrons because all elements desire a full octet (8 valence electrons). That being said, some elements are closer to a full octet by gaining electrons, whereas some are closer when they give up electrons.
As a general rule, as you move to the right across the period table, the number of valence electrons an element has increases. Therefore, on the right of the periodic table, these elements have a little less than 8 valence electrons. It makes sense that these elements want to gain those last few electrons to gain a full octet, rather than giving up electrons. Sulfur (S) has 6 valence electrons (located in the 16th column). To gain a full octet, it will gain two electrons and thus become an anion.
Na, Mn, and Ba are on the left of the periodic table, so they'd rather give up electrons than gain them (to become cations).