以下华为NE40E路由器更换部件的注意事项正确的是（）

A.一次只能更换一块交换网板。如果要更换多块交换网板，要先更换完一块，待新插入的交换网板正常运行后，再更新其它交换网板

B.在更换NE40E-X16设备下插板区的单板时，注意单板的安装方向和上插板区的安装方向相反

C.LUPF-20的03030GQU和03030HPS子卡不支持热插拔。由于结构特殊，在更换这两个子卡时，需要将LPUF-20母板拔出

D.更换风扇框时，在拔出旧风扇框的过程中，先将风扇拔出约5cm，待风扇停止转动后，再将风扇拔出

DOM is a platform and language- (51) API that allows programs and scripts to dynamically access and update the content, structure and style of WWW documents (currently, definitions for HTML and XML documents are part of the specification). The document can be further processed and the results of that processing can be incorporated back into the presented (52) . DOM is a (53) -based API to documents, which requires the whole document to be represented in (54) while processing it. A simpler alternative to DOM is the event-based SAX, which can be used to process very large (55) documents that do not fit info the memory available for processing.

A．text

B．image

C．page

D．graphic