Answer:
b. The price of coffee beans falls
Step-by-step explanation:
Only a decrease in price of coffee beans would lead to a fall in the quantity supplied of coffee beans.
This is in line with the law of supply which says: The higher the price, the higher the quantity supplied and the lower the price, the lower the quantity supplied.
The other factors listed in the options would lead to a fall in supply and not quantity supplied.
I hope my answer helps you