Neither of these are minerals, B.
Its not A because, they are not natural materials but instead made up of natural materials, like a rubber tree.
Its not C because, like I said, plastic is made from rubber trees, this garentees it doesnt have a crystal structure.
Its not D because, concrete is not a mineral and has indefinite composition.
 
        
             
        
        
        
Answer:
non-specific system
Explanation:
The non-specific immune system is the system that works 24 hours a day, 7 days a week and protects you, regardless of the organism you encounter. This system is composed of the general defenses of the organism that work continuously, creating barriers that protect the body from the entry of any pathogen or foreign substance. This system is composed of T cells, which are true killers of pathogens and which guarantee efficient and complete safety.
 
        
             
        
        
        
A mixture of equal amounts of two enantiomers  <span>is called a racemic mixture.</span>
        
                    
             
        
        
        
The
patellar reflex is the most common example or a spinal reflex. When the knee is
tapped, the nerve that will receives this stimulus sends an impulse to the
spinal cord and relay it to the motor nerve. This sources the quadriceps muscle
at the front of the thigh to contract and twitch up the leg. This reflex contains
simply two nerves and one synapse. The leg will start to twitch up on the other
hand the brain is just suitable aware of the tap and comprehends the situation.
<span>Subsequently the tap, the leg is routinely lengthy
once and comes to rest. The nonappearance of this reflex is problematical and recognized
as westphals sign this reflex might be lessened or absent in lower motor
neuron lesions and during sleep. </span>