（1）把AlCl3溶液蒸干，灼烧，最后得到的主要固体产物是______，Al2（

IT运营的应急计划应该包括适当的备份协议。当重要的操作需要立即获得计算机资源时，下面（）被认为是过度依赖于供应商。

A．热站 

B．冷站 

C．冷站和热站结合 

D．在组织内使用另—个数据中心的额外空间/容量

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．XML

B．HTML

C．script

D．Web

X线穿过均匀物质时，其衰减与下列哪一项因素有关（）

A、物质的衰减系数

B、物质与X线源的距离

C、X线的曝光时间

D、X线束的厚度

E、物质的面积

以下关于物理学常识，说法错误的是（）

A.汽车雾灯选择黄色是因为黄色穿透力较强

B.油罐车后的金属链条是为了将静电荷传到地面

C.天空看起来是蓝色，是因为大气中的空气分子对太阳光的折射作用

D.自来水管“出汗”是水蒸气液化的结果，常常是下雨的预兆

如何理解生物转化的复杂性？