Answer:
It says that momentum cannot be created or destroyed. Momentum just passes through systems as opposed to just disappearing in thin air. Momentum can be changed to heat or energy.
Explanation:
 
        
             
        
        
        
Answer: it is D. it is the only possible answer. use the process of elimination. which answers make sense?
 
        
             
        
        
        
Answer:
 Membrane potential
Explanation:
Membrane potential is describes the difference in electrical charge across a membrane.                                                                                                              
The difference in potential between exterior  and  interior of the  biological cell is known as Membrane potential.Generally it is denoted by  millivolts like mV and varies from -80 V to -40 V.
So the answer is Membrane potential
 
        
             
        
        
        
If you're listening to a sound that has a steady pitch, and suddenly the 
pitch goes up, then you know that two things could have happened:
EITHER ...
-- The person or other source making the sound could have 
raised the pitch of the sound being produced.
OR ...
-- The person or other source making the sound could have 
started moving toward you.
OR ...
-- both.
Even if the pitch of the sound leaving the source doesn't change, 
you would still hear it increase if the source starts moving toward 
you.  That's the so-called "Doppler effect".