Which of the Following Increases in Labor Demand Is Due

Which of the following increases in labor demand is due to a change in the product demand?

A) Access to computers increases the productivity of mail order businesses, thus increasing the demand for their workers.
B) Tourism increases in popularity, increasing the demand for workers at tourist resorts.
C) A decrease in the price of trucks decreases the cost of transporting goods, thus increasing the demand for truckers.
D) A change in work rules increases output per worker in the auto industry, thus increasing the demand for autoworkers.