根据票据法律制度的规定，下列各背书情形中，属于背书无效的有( )。 A．将汇票金额

下列物质 ①空气  ②红磷  ③四氧化三铁  ④石灰水  ⑤液氧  ⑥蒸馏水  ⑦高锰酸钾

属于混合物的是______ （填序号，下同），属于单质的是______，属于化合物的是______，属于氧化物的是______．

室外消火栓按其进水口连接形式可分为()。

（A）地上式和地下式 

（B）承插式和法兰式 

（C）单栓式和双栓式 

（D）普通式与特殊式

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．text

B．image

C．page

D．graphic

如果该公司使用后进先出法对存货估价，那么当年销货成本是（）

A．77500美元 

B．86250美元 

C．87500美元 

D．95000美元