Final answer:
Individuals who have had much (or even all) of their stomach removed can survive well with vitamin B12 injections. However, individuals cannot survive without the small intestine as it plays a crucial role in nutrient absorption.
Step-by-step explanation:
Individuals who have had much (or even all) of their stomach removed can survive well because the only stomach function necessary for life is the production of intrinsic factor. If individuals receive vitamin B12 injections, which is necessary for the absorption of vitamin B12, they can function normally.
As for the small intestine, it plays a crucial role in the absorption of nutrients. Without the small intestine, individuals would not be able to absorb nutrients like carbohydrates, proteins, and fats, leading to malnutrition and other health complications. Therefore, individuals cannot survive without the small intestine.