The Basis Theory in Using Spot Rates to Forecast Future

The basis theory in using spot rates to forecast future value of the currency is that:

A) markets are notoriously unpredictable,so trying to determine what a currency will be worth in the future is unreliable and the current value of the currency is as good as any guess.
B) over time,the spot rate of a currency determines the future value of the currency and it is easy and inexpensive to determine the spot rate of a currency.
C) market participants are considered to all relevant information in their current trading,so all information that can affect the future value of a currency is already factored into the value of the currency.
D) over time,the changes to the spot rate will be both positive and negative,so the spot rate,as somewhere near the average value of the currency over time,is a good estimation of the future value of the currency.