Two tall buildings are 30 m apart. The speed with which a ball must be thrown horizontally from a window 150 m above the ground in one building so that it enters a window 27.5 m from the ground in the other building is:

• A

  2 ${\mathrm{ms}}^{-1}$

• B

  $6 {\mathrm{ms}}^{-1}$

• C

  $4 {\mathrm{ms}}^{-1}$

• D

  $8 {\mathrm{ms}}^{-1}$