In which of the following processes is $\Delta S$ positive?

• A
  $H_2O_{(l)} \rightarrow H_2O_{(s)}$
• B
  $3O_{2(g)} \rightarrow 2O_{3(g)}$
• C
  $H_2O_{(l)} \rightarrow H_2O_{(g)}$
• D
  $N_{2(g)} + 3H_{2(g)} \rightarrow 2NH_{3(g)}$