Which of the Following Would Cause an Increase in the Supply

Multiple Choice

Which of the following would cause an increase in the supply of peanut butter?

A) a decrease in the price of grape jelly (assuming that peanut butter and grape jelly are complements)
B) an increase in the price of peanut butter
C) an increase the price of a product that producers sell instead of peanut butter
D) an increase in the number of firms that produce peanut butter