Final answer:
In order to achieve sedation with nitrous oxide, it is important to have a low concentration of nitrous oxide and a high concentration of oxygen.
Step-by-step explanation:
In order to achieve sedation with nitrous oxide, it is important to have a low concentration of nitrous oxide and a high concentration of oxygen. Respiratory problems can also make it more difficult to achieve sedation. Therefore, the correct answer is d) Both b and c.