I would said A is the best option if i’m wrong sorry
        
             
        
        
        
Answer:
This is because normal force is exerted perpendicularly to the point of contact between the upper and lower objects.  
Explanation:
This is because the upper object is still subject to gravitational pull. Therefore, the amount of force it exerts on the lower object due to gravity will be equal to the normal force that acts in the negative direction of gravitational force. Additionally, normal force is evident because the upper object will not go into the lower object. 
 
        
             
        
        
        
The correct answer is<span> B.The speed of sound in air is directly proportional to the temperature of the air.
When the temperature increases so does the speed of sound. Sound is faster by </span>0.60 m/s for every higher degree in air temperature because the air density is reduced and the sound can travel faster.
        
             
        
        
        
Answer:
The value is    or  21.45%
  or  21.45%
Explanation:
From the question we are told that 
     The first reservoir is at steam point   
   
     The  second reservoir is at room temperature 
Generally the  maximum theoretical efficiency of a Carnot engine  is mathematically evaluated as
      
 =>    
=>    