In the Specification of Adaptive Expectation Used in the Dynamic $\pi$

In the specification of adaptive expectation used in the dynamic model of aggregate demand and aggregate supply, people at time t - 1 forecast the inflation rate in time period t will be:

A) $\pi$ _{t - 2}
B) $\pi$ _{t - 1}
C) $\pi$ _t
D) $\pi$ _{t + 1}