Which of the Following Equations, Discussed in the Text, Can $i _ { t } = \bar { r }$

Which of the following equations, discussed in the text, can be used to predict the federal funds rate?

A) $i _ { t } = \bar { r }$
B) $i _ { t } = \bar { m } \left( \pi _ { t } - \bar { \pi } \right)$
C) $i _ { t } = \bar { r } + \bar { \pi } + \bar { m } \left( \pi _ { t } - \bar { \pi } \right)$
D) $i _ { t } = \bar { r } + \pi _ { t } + \bar { a }$
E) None of these answers are correct.