Concept:An increase in supply means producers offer more of a product at every given price, shown by a rightward shift of the supply curve.
Explanation:A change in taste and fashion of consumers affects demand, not supply.
An increase in the income of consumers also affects demand, not supply.
An increase in the price of a product causes a movement along the supply curve, not an increase in supply itself.
A fall in the cost of production reduces the expense of making the product, making production more profitable.
Therefore, producers are willing and able to supply more of the product at each price, increasing supply.
Answer:C. a fall in the cost of production