How should you signal the crane operator to use the main hoist?（）.

A.Use one hand to give any miotion signal , and place the other hand motionless in front of the hand giving the motion signal

B.Extend arm with the thumb pointing up , and flex the fingers in and out for as long as the load movement is desired

C.First tap your elbow with one hand , and then proceed to use regular signals

D.First tap the top of your head with your first , and then proceed to use regular signals

影响施工项目进度计划的内部因素不包括（）

A、土建工程工期延误

B、需用资金不能如期到位

C、施工设计不能按计划提供或设计作重大修改

D、施工方法失误造成返工