下面是2014年6月英语六级阅读真题长难句解析(17)，请考生仔细分析句子结构。
　　1. Finally, advertisers try to begin commercials with sounds that are highly different from those of the programming within which the commercial is buried. (1998. 阅读. 6. Text 3)
　　【译文】最后，广告商费尽心机使广告开始的声音不同于其他节目的声音。
　　【析句】复合句。主句advertisers try to begin commercials with sounds,随后是that引导定语从句that are highly different from those of the programming修饰sounds,而定语从句中the programming后也有which引导的定语从句修饰。
　　2. But the developing countries may be impoverished, with populations growing so rapidly that using the land is a means to temporarily avoid worsening poverty and starvation. (1998. 阅读. 6. Text 4)
　　【译文】但是，随着人口迅速增长，只能卖出土地以暂时避免贫苦和饥荒恶化，发展中国家可能会因此一贫如洗。
　　【析句】复合句。主句the developing countries may be impoverished,with populations growing so rapidly that...是with引导伴随状语。可以看出，with伴随状语中运用了so...that...词组，而that引导句子using the land is a means to avoid...。
　　3. And many naturally produced chemicals, though occurring in tiny amounts, prove in laboratory tests to be strong carcinogens-a substance which can cause cancer. (1999. 阅读. 1. Text 1)
　　【译文】尽管许多自然生成的化学物质分泌量极小，但实验证明却是强致癌物——可引起癌症的物质。
　　【析句】复合句。主句many naturally produced chemicals prove in laboratory tests to be strong carcinogens。主语many...chemicals后，though occurring in tiny amounts作让步状语从句，因为从句和主句主语相同，所以省略了主语。破折号后a substance是carcinogens的同位语，并且which can cause cancer作定语从句修饰a substance。