If, for John’s current intertemporal consumption pattern (satisfying his intertemporal budgetconstraint), his marginal rate of intertemporal substitution is 1 and the real rate of interest is positive, then...

• A. the interest rate will fall to zero.
• B. john could increase his lifetime utility by consuming more today.
• C. john could increase his lifetime utility by consuming less today.
• D. john is necessarily a borrower.