Some of the low-end Made-in-China mechanical-electronic products are not selling well in export market as compared with what are termed as high-end ones.

A．on export market

B．in exporting market

C．in exported market

D．in the export market

零件的缺陷在循环载荷作用下会逐渐扩大，当缺陷扩大到临界尺寸后将发生断裂破坏，这个过程称之为（）。

A.失效过程 

B.蠕变破坏过程 

C.磨损破坏过程 

D.疲劳断裂过程