Mountains is capitalized incorrectly
        
                    
             
        
        
        
The antecedent in the sentence is C
        
                    
             
        
        
        
"Then" is used in an "if-then" scenario, to dictate chronological order. In other words, "If you jump off, then you will fall," or "he was attacked and then retreated."
"Than" is used for comparisons. In other words, "The egg was bigger than the pea," or "I'm stronger than you."