DOM is a platform-and language-____(66)___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　incoporporated back into the presented ___(67)____.DOM is a ___(68)___-based API to　documents ,which requires the whole document to be represented in ____(69)___while　processing it .A simpler alternative to DOM is the event –based SAX,which can be　used to process very large ___(70)___documents that do not fit info the memory　available for processing.

（69）处填（）。

A．document

B．processor

C．disc

D．memory

如图所示，A与B质点的运动情况在V-t图像中，由A与B表示，则下述正确的是（）

At=1s时，B质点运动方向发生改变

Bt=2s时，A与B两质点间距离一定等于2m

C在t=4s时A与B相遇

DA与B同时由静止出发，朝相反的方向运动