Psychologists suggest that to cure cruelty

One of the differences between some whales and dolphins is that

1. 
   whales don't provide milk for their young, but dolphins do
   
2. 
   although dolphins have lungs for breathing, most whales don't
   
3. 
   while all dolphins are warm-blooded, whales are cold-blooded
   

D) whereas all dolphins have teeth, some whales don't have any

2. From the information given in the passage, we can infer that dolphins

1. 
   have difficulty surviving in captivity
   
2. 
   use only one lung at a time
   
3. 
   are among the largest marine animals
   
4. 
   don't breathe underwater