Answer: 
 Describe a recent activity or visit and say why it was successful.
Explanation:
 
        
                    
             
        
        
        
The appositive is a renaming of a noun, something that can be skipped without changing the grammatically and meaning of the sentence.  
Here the appositive is "Dr. Walters" - it can be skipped:
My dentist was one of the speakers at Career Day 
and it renames "My dentist" - answer B
        
             
        
        
        
Mark's television can't be plugged into a wall.
        
             
        
        
        
What exactly are you asking? im guessing this is a unfinished questions because there is no documents or anything attached just directions