重点调查的重点单位是指（）。

A．规模较大的企业

B．关乎国计民生的国有企业

C．垄断型企业

D．在所要调查的数量特征上占有较大比重的单位

How should you signal the crane operator to stop in an emergency?（）.

A.Extend arm with the palm down and and hold this position rigidly

B.Place clasped hands in frontof your body

C.extend arm and move hand rapidly right and left with the plam outward

D.Place both fists in front of the body with the thumbs pointing outward