Among All Unbiased Estimators That Are Weighted Averages Of $Y _ { 1 } , \ldots , Y _ { n } , \bar { Y }$

Multiple Choice

Among all unbiased estimators that are weighted averages of $Y _ { 1 } , \ldots , Y _ { n } , \bar { Y }$
is

A) the only consistent estimator of $\mu _ { Y }$
B) the most efficient estimator of $\mu _ { Y }$
C) a number which, by definition, cannot have a variance.
D) the most unbiased estimator of $\mu _ { Y }$