The correct answer is b) A president addressing the nation. 
Oration is a formal speech given usually at an official occasion, such as a president giving a speech. Orations are usually given at funerals, weddings, formal ceremonies, such as graduation, in the court of law, at conferences, inaugurations, etc. 
 
        
             
        
        
        
We/They must resolve the problem
 
        
             
        
        
        
P1 is the name of first seeds collected from <span>monohybrids</span>
        
                    
             
        
        
        
According to the paper, is the prepositional phrase. According is a preposition.