An aeroplane is flying with speed 60 m/s at angle 30^o with the horizontal. A shell is fired horizontally from the aeroplane. Find the direction and magnitude of velocity of the
shell so that it falls vertically along a straight line with respect to the observer on the ground. 

• A

  horizontally opposite to motion of plane with velocity $30\sqrt{3}\mathrm{m}/\mathrm{s}$

• B

  horizontally opposite to motion of plane with velocity 60 m/s

• C

  at angle 30^o with the horizontal opposite to motion of plane with velocity 60 m/s

• D

  at angle 30^o with the horizontal opposite to motion of plane with velocity $30\sqrt{3}\mathrm{m}/\mathrm{s}$.