The answer would be C: Rheostat.  :)
        
                    
             
        
        
        
Answer:
Mass as a Measure of the Amount of Inertia
All objects resist changes in their state of motion. All objects have this tendency - they have inertia.
Explanation:
hope this helps
 
        
             
        
        
        
It’s me again lol you’re questions are simple the formula is given in the triangle 
The answer is C 39 hz
Please look at the attached image below for the explanation
 
        
        
        
Answer:
1. the electromagnetic wave.
Explanation:
Mathematically, 
wavelength = velocity ÷ frequency
A mechanical wave is a wave that is not capable of transmitting its energy through a vacuum. Mechanical waves require a medium in order to transport their energy from one location to another. A sound wave is an example of a mechanical wave. Sound waves are incapable of traveling through a vacuum.
Electromagnetic waves of different frequency are called by different names since they have different sources and effects on matter, increasing frequency decreases wavelength.
Sound waves (which obviously travel at the speed of sound) are much slower than electromagnetic waves (which travel at the speed of light.)  
Electromagnetic waves are much faster than sound waves and If the Velocity of the wave increases and the frequency is constant, the wavelength also increases.