Answer:
<em>The correct option is cell surface markers.</em>
Explanation:
The immune cells of our body detect foreign particles and generate responses so that our body can get rid of them. The foreign particles are often termed as antigens.
The immune cells such as antibodies possess cell surface receptors which detect the foreign objects or antigens. When the cell surface receptors detect any antigen they immediately recognize that a foreign particle has invaded the body and they then identify it and start to generate response. 
 
        
             
        
        
        
Explanation:
The large fish will most likely eat most of the white fish, and there will only be gray fish left. Since the large fish can't see the gray fish well, they catch some but quickly starve because of the lack of white fish. In the end, only gray fish are left.
 
        
             
        
        
        
The earth is about 6,000 years old.
        
                    
             
        
        
        
Answer:
The answer is A. Fertilized ovules