Psychologists suggest that to cure cruelty

The main concern of the passage is

1. 
   how protoplasm is arranged into cells differently in plants and animals
   
2. 
   why all life forms should be classified into five major groups
   
3. 
   why plants manage to feed themselves but life forms in animal kingdom don't
   

D) the difficulty of giving a definition separating plants from other life forms

2. We understand from the passage that protoplasm

1. 
   is a simple life form
   
2. 
   is a method of grouping life forms
   
3. 
   is a separate life form
   
4. 
   contains cells
   

3. The current method of classifying life forms involves

1. 
   separating the plant and animal kingdoms
   
2. 
   taking significant differences in cell formation into account
   
3. 
   seeing if an organism contains green coloring
   
4. 
   noting if an organism can produce food chemically