Since the stone is travelling, the displacement cannot be constant. This leaves the last 2 choices as possibilities. Now consider the acceleration that can act on the stone. Acceleration due to gravity is the only one. That means the horizontal component of the stone has to be constant since there is no acceleration in the horizontal direction.
B. A hypothesis is just an idea. And can become a Theory if there is some evidence. However a Theory is not a law, but an idea with supportive evidence
The physical law that explains that is the law of conservation of energy which states that he energy of an isolated sistem remains constant
Acceleration x time = velocity
Since you're given acceleration and time, just plug the values into the equation.
3

x 1.1 s = ?
Solve that equation, and remember your velocity should be in m/s.