Rank the nonmetals in each set from most reactive (1) to least reactive (3).
Neon
Selenium
Fluorine:

The reactivity for the metal atoms in the periodic table increases as we go down a group and move from right to the left across a period. However, for non-metals the situation is opposite. The reactivity of non-metals decreases down a group and the reactivity also decreases when we move  from right to left across a period. Hence, we can rant the above elements as follows:

Fluorine

Selenium

Neon

c) troops march forward in close formation against newer, more accurate weapons