如图3.7.2.6所示扩展基础，柱截面400mm×400mm，基础底面2400mm×2400mm，基础埋深1.5m，基础高度h=600mm，两个台阶，上台阶两个边长均为1100mm，h₀=550mm，h₀₁=250mm，f_t=1.1N/mm²，基础顶面受到相应于荷载效应基本组合时的竖向力设计值F=680kN。

变阶处抗冲切承载力为（）kN。

A．336.91

B．404.29

C．259.9

D．311.88

DOM is a platform-and language- (71) API that allows programs and scripts todynamically access and update the content． structure and style of WWW documents(currently，definitions for HTML and XML documents are part ofthe specification)．Thedocument can be further processed and the results of that processing can be incorporated backinto the presented (72) ．DOM is a (73) -based API to documents，which requires the wholedocument to be represented in (74) while processing it．A simpler altemative to DOM is the event—based SAX，which can be used to process very large (75) documents that do not fitinfo the memory available for processing．

A．table
B．tree
C．control
D．event