Defining $Y _ { t }$ As Current Output $\bar { Y } _ { t }$

Defining $Y _ { t }$ as current output, $\bar { Y } _ { t }$
As potential output, and $\tilde { Y } _ { t }$
As short-run fluctuations, which of the following equations is correct?

A) $Y _ { t } = \tilde { Y } _ { t } - \bar { Y } _ { t }$
B) $Y _ { t } = \bar { Y } _ { t } + \tilde { Y } _ { t }$
C) $\bar { Y } _ { t } = \tilde { Y } _ { t }$
D) $Y _ { t } = 0$
E) $Y _ { t } = \frac { \tilde { Y } _ { t } } { \bar { Y } _ { t } }$