Which of the following might cause an increase in supply?
a. Chips Unlimited unveils a new flavor, barbeque, which has students intrigued.
b. Researchers develop a higher - yielding, insect - repellant strain of rice.
c. During the Great Recession, the average income for an American worker fell sharply. Americans reduced their visits to restaurants.
d. The price of goose feathers, an input for pillows, increases sharply.