阅读图文材料，完成下列要求。（22分）

一位被热带雨林风光吸引的游客从马瑙斯出发，乘船沿内格罗河（图6）溯源而上，见两岸植被繁茂，河上很少有桥。行至内格罗河与布朗库河交汇处，发现两条河流的河水因颜色迥异，呈一黑黄分明的界限，景色令人震撼。船继续前行，岸边的沼泽渐渐映入眼帘……当晚他查阅资料，得知内格罗河河水因富含腐殖质，颜色乌黑，而布朗库河因含大量泥沙而呈黄色。

（1）分析内格罗河河水富含腐殖质但泥沙含量少的原因。（8分）

（2）试对“河上很少有桥”这一现象作出合理解释。（8分）

（3）你是否赞同在该地区拓展旅游观光业？请标明态度并说明理由。（6分）

Bluetooth is a universal radio interface in the (1) frequency hand that enables portable electronic devices to connect and communicate wirelessly via short-range, ad hoc networks. Each unit can simultaneously communicate with up to (2) other units per piconet. Moreover, each unit can simultaneously (3) to several piconets. Eliminates the need for wires, cables and connectors for and between cordless or mobile phones, modems, headsets, PDAs, Computers, printers, projectors, local area networks, and so on, and paves the way for new and completely different devices and applications. Technology Characteristics (4) symbol rate exploits maximum available (5) bandwidth。

3（）

A．conformance

B．relate

C．belong

D．secrecy