Answer:
d. future income is worth less than present income
Step-by-step explanation:
Remember, since we want an exception to all the possible reasons for higher salaries of those in medical and architectural profession, we carefully examine the reasons given.
However, in no way is it because those of this profession (architect, medical doctors) would earn future income worth less than their present income a basis for their higher salaries than other jobs, since most often they earn more as they the years goes by in their profession.