题干
She promised to be here at 8:00, but she never ______.
A：turned dow
B：turned off
C：turned over
D：turned u
答案(点此获取答案解析）
D
A：turned dow
B：turned off
C：turned over
D：turned u
表示从树突到胞体再到轴突及末梢（即一个完整的神经元模式）。图2表示突触的显微结构模式图。下列关于图解的说法正确的是