In the Fixed Time Effects Regression Model, You Should Exclude

In the Fixed Time Effects regression model, you should exclude one of the binary variables for the time periods when an intercept is present in the equation

A) because the first time period must always excluded from your data set.
B) because there are already too many coefficients to estimate.
C) to avoid perfect multicollinearity.
D) to allow for some changes between time periods to take place.