The (29) is a general description of the architecture of a workflow management system used by the WFMC, in which the main components and the associated interfaces are summarized. The workflow enactment service is the heart of a workflow system which consists of several (30) 。

30（）

A. workflow engines

B. processes

C. workflow threads

D. tasks

扁平苔藓的组织病理变化是（）

A.色素增多

B.色素减少

C.色素失禁

D.表皮萎缩

E.疣状增生