The Denominator of the Appropriate Test Statistic for Testing for the Joint

The denominator of the appropriate test statistic for testing for the joint significance of a subset of independent variables is

A) $\left( U S S _ { \text {restricted } } - U _ { \text {SS } } S _ { \text {unrestricted } } \right) / q .$
B) $\left( U S S _ { \text {unrestricted } } - U S S _ { \text {restricted } } \right) / q .$
C) $\text { USS } S _ { \text {unrestricted } } / ( n - k - 1 )$
D) $U _ { S S _ { \text {restricted } } / ( n - k - 1 ) }$