Which of the following pairs of solutions is isotonic? (Molar mass: urea $= 60 \ g \ mol^{-1}$,sucrose $= 342 \ g \ mol^{-1}$)

• A
  $3.0 \ g \ L^{-1}$ urea and $17.19 \ g \ L^{-1}$ sucrose
• B
  $0.3 \ g \ L^{-1}$ urea and $1.719 \ g \ L^{-1}$ sucrose
• C
  $3.0 \ g \ L^{-1}$ urea and $1.719 \ g \ L^{-1}$ sucrose
• D
  $0.3 \ g \ L^{-1}$ urea and $17.19 \ g \ L^{-1}$ sucrose