Crossing over? That involves the random exchange of chromosomes. 
        
             
        
        
        
After a caterpillar eats a leaf, it can convert the chemical energy into mechanical energy to help it build a cocoon.
        
             
        
        
        
Answer:
The correct option is D. New cells are produced from existing cells is a part of the cell theory.
Explanation:
Cell theory can be described as one of the earliest theories of biology which states that cells are the basic unit of life out of which all living things are made. The modern cell theory comprises of three main parts:
- All the living forms of life are manufactured from cells.
- Cells are the main unit which are involved in properly organizing a living organism.
- New cells arise from pre-existing cells.
 
        
             
        
        
        
Answer:
Food must be broken down into nutrients for the body to use for energy, development, and cell repair. Before the blood absorbs and transports nutrients to cells in the body, food and drink must be broken down into smaller nutrient molecules.