Remember opposites attract and same charges repel each other. 
Object A= negatively charged.
Object A and B attract so B must be positively charged.
Object B and C repel so because B is positively charged C must also be positively charged.
Object C and D attract and because C is positively charged, D must be negatively charged.
 
        
             
        
        
        
Answer:These two forces are called action and reaction forces and are the subject of Newton's third law of motion. Formally stated, Newton's third law is: For every action, there is an equal and opposite reaction. The statement means that in every interaction, there is a pair of forces acting on the two interacting objects.
Explanation:
 
        
             
        
        
        
Answer:
Volume of given mass of gas is inversely proportional to pressure of gas
Explanation:
Boyle's law: It states that the volume of given mass of gas is inversely proportional  to the pressure of gas at constant temperature.
Mathematical representation:
Suppose, a gas of mass m
 T=Constant temperature
V=Volume of gas
P=Pressure of gas
Then, 