Just can serve as a abstract noun itself, Justice can also be used
        
             
        
        
        
My mother telephoned my sister and said "I (or you) won a trip to Ireland"
        
             
        
        
        
Answer:
adjective
Explanation:
Moment is a noun, and adjectives modify nouns/pronouns. Since serene modifies moment, it is an adjective. 
 
        
             
        
        
        
Answer:
A
Explanation:
I did the test and got it right. Hope this helped.