Which of the Following Would Cause an Increase in the Supply

Which of the following would cause an increase in the supply of hot-air balloon rides?

A) an increase in the demand for hot-air balloon rides
B) an increase in the cost of fabric used to make balloons
C) a decrease in the wages of hot-air balloon pilots
D) an increase in the price of hot-air balloon package delivery services, a substitute in production for hot-air balloon rides