Mercury Is more suitable than water cause it is denser than water. 
Relation between density and pressure
Pressure = force/area
Replace force by mass * acceleration 
Pressure = mass * acceleration/ area
We can replace mass by density * volume since density = mass/ volume
Pressure = density * volume * acceleration/ area
Volume is length^3 whereas area is length ^2. So volume / area = length
Pressure = density * length * acceleration
Gravity is form of acceleration so
Pressure = density * length * gravity
Length can be height or depth
Finally pressure = density * height * gravity
P = ρ g h => pressure of liquid
        
             
        
        
        
It has to be D because the arrow will drop as it moves, if it were a gun, you'd lead the target so fire below it, but due to it being an arrow, you aim high not low. Also, they didnt specify how fast anything is, so you'd probably miss if you actually did it.
 
        
                    
             
        
        
        
Answer:
1.  F = M x A
2. Force  
3. 2nd Law: Force
4. a, b, c (in order)
5. 3rd Law: Action and Reaction
6. b, c, a (in order)
7. 1st Law: Inertia 
 
        
                    
             
        
        
        
Answer and Explanation:
This experiment is known as Lenz's tube.
The Lenz tube is an experiment that shows how you can brake a magnetic dipole that goes down a tube that conducts electric current. The magnet, when falling, along with its magnetic field, will generate variations in the magnetic field flux within the tube. These variations create an emf induced according to Faraday's Law:

This emf induced on the surface of the tube generates a current within it according to Ohm's Law:

This emf and current oppose the flux change, therefore a field will be produced in such a direction that the magnet is repelled from below and is attracted from above. The magnitude of the flux at the bottom of the magnet increases from the point of view of the tube, and at the top it decreases. Therefore, two "magnets" are generated under and above the dipole, which repel it below and attract above. Finally, the dipole feels a force in the opposite direction to the direction of fall, therefore it falls with less speed.