Mr. c. freely admits he enjoys food – lots of food, mostly rich food, and food that isn't necessarily healthy. his lunch companion assures him that he can still enjoy food but just needs to pick foods that deliver the most nutrients for the fewest kcalories. such foods are termed:

Such foods are termed as Nutrient dense foods. 
Nutrient dense foods are foods that have a lot of nutrients but relatively few calories. They contain vitamins, minerals, complex carbohydrates, lean protein, and healthy fats. Examples of nutrient dense foods include fruits and vegetables, whole grains, low-fat or fat-free milk products, sea food among others.

Cell division is important to single celled organisms because it allows the cells to reproduce. through cell division, cells make exact copies of themselves. when single celled organisms go through cell division, they make exact copies of themselves which is how they reproduce.