All the following statements regarding creating of time estimates are correct EXCEPT:

A．Mathematical analysis like CPM, GERT and PERT indicate the dates in which the activity can be scheduled given resource limits and other constraint

B．Duration compression techniques including fast tracking and crashing can help in decreasing the project schedul

C．WBS classification allows for useful activity ordering and sortin

D．The duration of the project is the sum of durations for all the tasks in the projec

三聚氰胺是一种化工原料，不可用于食品添加剂。三聚氰胺的分子式为C₃H₆N₆，它属于 [ ]

A．单质

B．有机物

C．混合物

D．氧化物