I think it's C. Heavy means the sigh was long, and obviously loud. Wind through a tomb is used as a metaphor that the sigh was lonely. Lonely means nobody is there, and nobody is there to hear wind go though a tomb, and anyone in the tomb can't hear, because, well, they're dead. 
        
                    
             
        
        
        
There are two meanings for Strand. 
one is <span>drive or leave (a boat, sailor, or sea creature) aground on a shore.
another is </span><span>the shore of a sea, lake, or large river.
</span><span>sprang - move or jump suddenly or rapidly upward or forward. verb
</span> 
        
                    
             
        
        
        
It adds emphasis shows how common it is for them
        
             
        
        
        
A
It was to attract more settlers to the area.