Answer:
a. the RNA polymerase undergoes abortive initiation prior to promoter clearance
Explanation:
In eukaryotes the 3' end of the mRNA is polyadenylated to protect the mRNA from degradation. 
In eukaryotes, a modified guanine cap is added to the 5' end of the mRNAd to protects the transcript from being broken down. 
Most bacterial RNA transcripts do not undergo splicing.
The nucleosome is the basic unit of chromatin repeat in eukaryotes.
 
        
             
        
        
        
There aren't enough oxygen molecules in the air are higher altitudes
        
                    
             
        
        
        
answer of the question: B
 
        
                    
             
        
        
        
The Most appropriate answer is A !!