Which of the Following Is a Reason for the Failure

Which of the following is a reason for the failure of PPP to predict exchange rates accurately?

A) PPP takes transportation costs into consideration while predicting exchange rates.
B) PPP assumes no barriers to international trade while predicting exchange rates.
C) PPP considers the role of people's confidence and beliefs about a nation's economy in exchange rate predictions.
D) PPP does not take into account the effect of the market forces of demand and supply.