Q1. An elderly man has been receiving weekly injections of vitamin B12 ever since nearly all of his stomach was removed 6 months ago due to stomach cancer. Why is he receiving the vitamin injections? Why can’t the vitamin be delivered in tablet form? What is function of the vitamin in hematopoiesis?

Q2. Why could prokaryotes quickly reinfect a patient if they are not wiped out? How may this result in the evolution of drug-resistant pathogens?