Answer :
projectile can only follow the straight line path when it is launched upward straightly so the correct option is 90 degree with respect to horizontal x -axis ..:)
Answer:
90 degree
Explanation:
For the horizontal projection or the vertical projection, the path traversed by the projectile is a straight line .
So the angle of projection is 0 degree or 90 degree.
In this condition the motion is in one dimension. If the angle of projection is any arbitrary angle except 0 degree or 90 degree, the motion of the projectile is parabolic.