This problem is said_____ three times at the meeting. However, they haven’t arrived at a conclusion now.

A．to have discussed

B．to have been discussed

C．having been discussed

D．having discussed

（）如零件局部热处理或局部镀（涂）时，应用划出范围，并注出相应的尺寸说明。

A.细实线

B.粗实线

C.点画线

D.虚线