The Denominator of the F Ratio Used to Test the Main

The denominator of the F ratio used to test the main effect of factor A in a two-factor ANOVA is MS_AB in which one of the following?

A) Fixed-effects model
B) Mixed-effects model where A is the fixed factor
C) Mixed-effects model where A is the random factor
D) Split-plot model where A is the between-subjects factor
E) Split-plot model where A is the within-subjects factor