Answer: I would say it would be 3.9 
 but i believe there is something missing shorty.
 
        
             
        
        
        
Answer:
The types of solenoids are: AC Laminated Solenoid
, DC Solenoid
, Linear Solenoid
,and Rotary Solenoid. 
Explanation:
- The main purpose of solenoid is to generate the controlled magnetic field that can be used in many forms.
- The most common use of solenoid is done in the pinball game.
- The Flipper solenoid that uses the two coil are used in the mechanism of pinball machines.
- One coil of the solenoid is supplied with high electric current where as other one has the weak current flowing through it.
 
        
             
        
        
        
Answer A is incorrect
A crest is just one point. It is not the distance between 2 crests.
B  is incorrect
A trough is just 1 point. It is not the distance between 2 troughs.
C is incorrect.
the amplitude measures the height of a crest from the middle of the wave to the crest (or trough).
D is the correct answer. That is the distance between 2 crests or 2 troughs 
        
             
        
        
        
The average speed between 0 h and 2.340 h is 6.97 Km/h
Average speed is defined as the total distance travelled divided by the total time taken to cover the distance. 

With the above formula, we can obtain the average speed between 0 h and 2.340 h as illustrated below:
- Total time = 2.340 – 0 = 2.340 h
- Total distance = 16.3 – 0 = 16.3 Km
- Average speed =? 

Learn more about average speed: brainly.com/question/24884027