Design of Experiments — correct error term in a two-way random effects ANOVA

Consider the random effect model for a two-way classified data with $m$ observations per cell. Which of the following statements is/are correct? I. Mean sum of squares due to error is used as error variance for computing the test statistics for $H_{0(A \times B)} : \sigma^2_{ab} = 0$. II. Mean sum of squares due to error is used as error variance for computing the test statistics for $H_{0A} : \sigma^2_a = 0$. III. Mean sum of squares due to error is used as error variance for computing the test statistics for $H_{0B} : \sigma^2_b = 0$. Select the answer using the code given below.