The project alongside with the experiment we had once devoted so much time__________ perfectly.

A．to work out

B．to working out

C．to worked out

D．has worked out

_________或___________以及套在外面的________叫神经纤维。在周围神经系统中，神经纤维聚集成为_____________，在中枢神经系统中，神经纤维聚集成为____________。