$5.0 \ g$ of sodium hydroxide (Molar mass $40 \ g \ mol^{-1}$) is dissolved in a small quantity of water and the solution is diluted up to $100 \ mL$. What is the molarity of the resulting solution?

• A
  $0.1 \ mol \ dm^{-3}$
• B
  $1.0 \ mol \ dm^{-3}$
• C
  $0.125 \ mol \ dm^{-3}$
• D
  $1.25 \ mol \ dm^{-3}$