I think this is the answer hope it helps
 
        
        
        
Let the mass of the person be m. Total momentum is conserved (because the exterior forces on the system are balanced), especially the component in the vertical direction. 
Given that, 
Mass of gallon is M
Let man mass be m
Velocity of man is v
Let velocity if ballot be Vb
When the person begin to move we have
Conservation of momentum 
mv + MVb=0
MVb=-mv
Vb= -(m/M) v
Given that the mass of man is less than mass of balloon. i.e. m<M
So, if m<M, then, m/M <1
Therefore, .
Vb= -(m/M) v
Vb< -v
This implies that the velocity of balloon is less than the velocity of man and if is also moving in opposite direction 
So the man is moving upward, then the balloon is moving downward and it's velocity is less than the velocity of man, 
The answer is C
Down with a speed less than v
 
        
                    
             
        
        
        
Answer:
In physics and chemistry, the law of conservation of energy states that the total energy of an isolated system remains constant; it is said to be conserved over time. ... For instance, chemical energy is converted to kinetic energy when a stick of dynamite explodes.
 
        
             
        
        
        
Construction, like building a home/building, digging, like in a mine, and opening a soda can, where the part to open is a lever.
        
             
        
        
        
A solid, liquid, or gas or plasma. Which I think it is. Check though.