聚丙烯放料阀回讯器凸轮松动时,影响其它釜继续输送粉料。

How should you signal the crane operator to dog everthing?（）.

A.Place both fists in front of the body with the thumbs pointing outward each other

B.Clasp hands in front of your body

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

D.Extend arm with the thumb pointing up, and flex the finger s in and out