Gustavo graduates from college and his income increases by $30,000. Nothing else changes. Gustavo decreases the quantity of T-shirts and chocolate chip cookies that he buys and increases the quantity of ski trips that he buys. How would Gustavo describe these goods? For Gustavo, O A. T-shirts and ski trips have become substitutes O B. T-shirts and chocolate chip cookies are normal goods O C. ski trips and chocolate chip cookies are normal goods OD. T-shirts and chocolate chip cookies are inferior goods