When I entered the room, I found a little boy _____ on his mother’s knees _____ to draw a picture.

A．seated; learning

B．sitting; to learn

C．seating; learning

D．sat; was learning

在一般情况下，以下关于调查研究中抽样误差的说法正确的是（）

A.整群抽样≥系统抽样≥单纯随机抽样≥分层抽样

B.系统抽样≥单纯随机抽样≥整群抽样≥分层抽样

C.分层抽样≥系统抽样≥单纯随机抽样≥整群抽样

D.整群抽样≥单纯随机抽样≥系统抽样≥分层抽样

E.单纯随机抽样≥整群抽样≥分层抽样≥系统抽样