Identify the reaction/process in which the entropy decreases.

• A
  $H_2O(l) \longrightarrow H_2O(s)$
• B
  $H_2O(l) \longrightarrow H_2O(g)$
• C
  $H_2O(g) \longrightarrow 2H(g) + O(g)$
• D
  Crystal $(100 \ K)$ $\longrightarrow$ Crystal $(200 \ K)$