I’m not an expert but I’d say B
        
             
        
        
        
There are so many examples for that in different areas, like biology experiment carried out in our lab recently.
Here's one link: https://www.creative-biogene.com/Robust-Tn5-Transposase-EMQZ1422-1271506-26.html
 
        
             
        
        
        
Answer:
pericardium
Explanation:
A double-walled membrane, the pericardium, separates the right and left chambers, preventing oxygen-rich blood from mixing up with the one without oxygen. So, the heart functions go smoothly. Deoxygenated blood enters the right atrium.