Definition: a supposition or proposed explanation made on the basis of limited evidence as a starting point for further investigation.
        
                    
             
        
        
        
The whistling sound from the hearing aids represents that your hearing aids is working perfectly ad is known as the "feedback". So, the given statement is true.
Answer: Option A
<u>Explanation:</u>
It's often sounds irritating when a hearing aids of your grandpa or Grandma whistles. especially, when they put them out of their ears. Actually, this feedback sound from hearing aids occur when the sounds from the outer side  bounces back to the microphone of the hearing aids.
The sound bounces back when it doesn't gets inside of your ear canal so that one can hear the sound through the hearing aid. When the sounds bounces back in the hearing aid, it get re-amplified and thus we hear the whistle sound which is known as the feedback of the device.
It's not always the feedback sound though. Sometimes the device whistles when it has some mechanical defect or when one hugs the other one or water gets inside and damaged the whole system.
 
        
             
        
        
        
Explanation:
it holds protons and neutrons together
 
        
             
        
        
        
If a car increases its speed from 20km/h to 100 km/h undergoes positive acceleration. Hope this helped!
        
             
        
        
        
Q stands for heat energy (Joules) hope this helps!