Cnidarians have specialized cells known as cnidocytes (“stinging cells”) containing organelles called nematocysts. These cells are concentrated around the mouth and tentacles of the animal and can immobilize prey with toxins. Nematocysts contain coiled threads that may bear barbs.
        
             
        
        
        
Answer: the tree main features of a synovial joint are articular capsule, articular cartilage and synovial fluid.
Explanation:
 
        
             
        
        
        
<h3><u>Answer;</u></h3>
B 
<h3><u>Explanation;</u></h3>
- Smooth muscle is found in the walls of hollow organs throughout the body. 
- Smooth muscle contractions are involuntary movements triggered by impulses that travel through the autonomic nervous system to the smooth muscle tissue.
- <u>The smooth muscle of the alimentary canal or the digestive tract facilitates the peristaltic waves that move swallowed food and nutrients.</u>
 
        
        
        
El teme son up poco differente porque hay differentes lados