Over the past two years, a firm reported higher operating cash flow as a result of securitizing its accounts receivable and from increasing income tax benefits from employee stock options. The tax benefits are solely the result of higher tax rates. Should an analyst conclude that these two sources of operating cash flow are sustainable()

A. Both sources are sustainable.

B. Neither source is sustainable.

C. Only one of these sources is sustainable.

据中国互联网信息中心统计，截至2011年12月底，我国微博用户达到2．5亿，占网民总数的48．7%，政府部门通过认证的新浪微博覆盖了全国所有省、自治区、直辖市和特别行政区。微博在多起公共事件和公共讨论中，充分展现其及时传播信息、快捷发布言论和反馈舆情的功能。对此有网民认为：微博是健康的现代沟通渠道。

（1）请选择一个最恰当的唯物辩证法原理，评析材料中网民的观点。

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（2）结合材料，运用《政治生活》的知识，说明如何用好微博。

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