The periodic trend of chemical reactivity for alkali metals and halogens is described in the following statements. Which statement provides the correct concept?

• A
  Reactivity decreases in alkali metals,but it increases in halogens with an increase in atomic number down the group.
• B
  Reactivity decreases in both alkali metals and halogens with an increase in atomic number down the group.
• C
  Reactivity increases in both alkali metals and halogens with an increase in atomic number down the group.
• D
  Reactivity increases in alkali metals,but it decreases in halogens with an increase in atomic number down the group.