Which of the following would unambiguously cause a decrease in the equilibrium price of cotton shirts?

A、an increase in the price of wool shirts and a decrease in the price of raw cotton;
B、a decrease in the price of wool shirts and a decrease in the price of raw cotton.;
C、an increase in the price of wool shirts and an increase in the price of raw cotton.;
D、a decrease in the price of wool shirts and an increase in the price of raw cotton.