尤文肉瘤主要成分来源是（）。

A.成骨细胞

B.成纤维细胞

C.成软骨细胞

D.骨髓细胞

E.破骨细胞

--- Did Mary attend the meeting on time yesterday?

--- No,she ______late as usual ,which made the boss very angry.

A．turned up

B．turned down

C．turned off

D．turned out