The Heteroskedasticity-Robust Estimator Of $\sum \sqrt { n ( \hat { \beta } - \beta ) }$

Multiple Choice

The heteroskedasticity-robust estimator of $\sum \sqrt { n ( \hat { \beta } - \beta ) }$ is obtained

A) from ( $X ^ { \prime }$ X) ^-1 $X ^ { \prime }$ ^U.
B) by replacing the population moments in its definition by the identity matrix.
C) from feasible GLS estimation.
D) by replacing the population moments in its definition by sample moments.