Answer:
1. Both Hydrogen should be positive and Oxygen is negative. I can't tell which photo that would represent however my best guess would be #2.
2. D
3. A
 
        
             
        
        
        
20 toes frogs normally have 7 toes on there fore limbs and 3 on their hind limbs
        
                    
             
        
        
        
I'm gonna go with D. dichotomous key because I believe the other ones are right and D is not related.
 
        
             
        
        
        
10. DNA is to T as RNA is to U.
11. DNA is to deoxyribose as RNA is to ribose.