Internal costs are easy to see and explain. They are costs that a business bases its price on. They include costs like materials, energy, labour, plant, equipment and overheads. External costs are costs that are NOT included in what the business bases its price on.
Because when you put a part of the DNA and take it out, you can restrict an ability of that cell. When you cut out a piece of DNA from a pancreas beta cell that codes for insulin synthesis, you restrict the cells ability to make insulin, hence the name "restriction enzyme". I hope this is the answer that you are looking for and it comes to your help.
D. ; Eukaryotic cells are bigger, younger, and more complex
Usually microorganisms help keep the nutrients in the soil cycling allowing for nutrients to be distributed all over. But they do what they can unless the disease is damaging to the soil itself therefore damaging the microorganisms working to keep the plant functioning.
