Similarities: 
They contain nematocyst (cells that sting)  
some are sessil/free swimming  
Some corals have a symbiotic relationship with algae, they need to grow in shallow waters so that light can penetrate for the algae to photosynthesize.
 
        
             
        
        
        
Answer: Purine; is equal to; pyrimidine
Explanation:
When a segment of DNA is examined then the nucleotide in one DNA molecule, it will be expected that the sum of purine in one strand will be equal to the sum of the pyrimidine in the other strand. 
Adenine combines with Thymine and Cytosine combines with Guanine in 1:1 ratio.
More specifically the ratio of purine is to pyramidine is 1:1 in an organism. This pattern is seen in both the strands of the DNA.
 
        
             
        
        
        
Answer: A, B, and D
Explanation: I just took the test