青春期龈炎牙龈表现为 A．龋增生，呈细小分叶状 B．跟呈瘤样突起，有蒂、鲜红、质软

有关双代号网络计划图绘制原则的表述，说法正确的有（）。

A.网络计划图必须按照已定的逻辑关系绘制

B.除终点和起点节点外，不允许出现没有内向箭线的节点和没有外向箭线的节点

C.网络计划图中所有节点都必须编号，并应使箭尾节点的代号小于箭头节点的代号

D.网络计划图中不允许出现从一个节点出发顺箭线方向又回到原出发点的循环回路

E.不允许在网络计划图中出现工作箭线交叉现象

DOM is a platform-and language- (1) 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 (2) . DOM is a (3) -based API to documents, which requires the whole document to be represented in (4) while processing it. A simpler alternative to DOM is the event-based SAX, which can be used to process very large (5) documents that do not fit into the memory available for processing.

A．document

B．processor

C．disc

D．memory

副驾驶一侧的红色T形手柄的作用

A、应急放起落架

B、应急释放起落架后，复位系统

C、应急刹车

D、应急放起落架储压瓶过压时，释放压力

增大接地网的（）是减小接地电阻的主要因素。

A、深度

B、导体截面积

C、面积

D、体积

真空系统不允许有丝毫泄漏。