A girl standing on road holds her umbrella at $45°$ with the vertical to keep the rain away. If she starts running without umbrella with a speed of $15\sqrt{2} \mathrm{km} {\mathrm{h}}^{-1}$, the rain drops hit her head vertically. The speed of rain drops with respect to the moving girl is

• A

  $30 \mathrm{km} {\mathrm{h}}^{-1}$
• B

  $\frac{25}{\sqrt{2}} \mathrm{km} {\mathrm{h}}^{-1}$
• Correct answer
  C

  $\frac{30}{\sqrt{2}} \mathrm{km} {\mathrm{h}}^{-1}$
• D

  $25 \mathrm{km} {\mathrm{h}}^{-1}$

Hence, the correct answer is option: 'C'.