I think that would be neurons
        
             
        
        
        
Answer:
A
Explanation:
There is no much more to say than the letter A describes the process of facilitated diffusion. 
The normal diffusion ocurres when the solute passes the membrane through the space of the double layer of phospholipids. Particles that are small and apolar can pass trough the membrane without problems.
For bigger or polar particles we need to use a protein system to help them pass into the cytoplasm. That's what we call Facilitated Difusion.
About the other options:
B) That's the explanation about active transport. That happen for every particle who is going against the gradient of concentration. 
C) Again: if we are talking about diffusion, there is no energy needed.
D) The Water Molecules suffer the process os osmotic pressure. Water deslocates to the higher gradient of concentration - contraty what the other particles do.
 
        
             
        
        
        
Answer:
B. Metamorphic
Explanation:
Metamorphic rock is combination of different rocks and builds off pre-existing rocks. This creates layers.
 
        
                    
             
        
        
        
Answer:
covalent bond 
it has 1 (outer most shell)
it has 7 (outter most shell)
hydrogen gains 1 chlorine gains 1
Explanation:
covalent bond as atoms share electrons to achieve full outer shell if electrons
hydrogen gains one to achieve 2 electrons in outer shell
chlorine gains 1 to achieve 8 electrons in outer shell 
 
        
             
        
        
        
The answer is C=territoriality
This is so because Al's cat may have seen another cat in his 'home'. Cats don't like it when other cats trespass into their territory, so this is a way of marking it.