What is the most likely reason for the development of a vitamin b12 deficiency ?

What is the answer to this particular question i have in health

Make a prediction about that person’s wellness and justify your prediction using two or more complete sentences.

Which statement best illustrates that problem solving can create new medical devices? robert hooke was in charge of verifying the information that was sent to the royal academy. william harvey did experiments with apes to learn about the circulatory system. the stethoscope was invented because the physician did not want to put his head on women's chests to listen to their heart and lungs. anton van leeuwenhoek was a very curious man and looked at just about everything under this microscope.