The GLS Assumptions Include All of the Following, with the Exception

Multiple Choice

The GLS assumptions include all of the following, with the exception of

A) the X_i are fixed in repeated samples.
B) X_i and u_i have nonzero finite fourth moments.
C) E(U $U'$ $|X$ ) = ?(X) , where ?(X) is n × n matrix-valued that can depend on X.
D) E(U $|X$ ) = 0_n.