Answer: 
a. 4 sig figs 
b. 3 sig figs
c. 2 sig figs
        
             
        
        
        
1. Publishing work in journals
2. Publishing on blog sites
3. Publishing with magazines and newspapers
4. Present at public lectures
        
             
        
        
        
where are the element you haven't showed it so that we can answer it 
 
        
             
        
        
        
Ummmmmmmmmmmmmmmmmmmmmmmmm, 21