抽样调查，确定样本数目多少，主要取决于（）。
A.费用开支的大小
B.调查结果的准确性要求
C.母体幅度大小
D.允许误差的大小
参考答案：C
—Was it under the tree _______ you were away talking to a friend?
—Sure. But when I got back there, the bike was gone.
A．that
B．where
C．which
D．while
ETF结合了封闭式基金与契约型基金的运作特点。( )
