句子主干是it will pass through sharp metal bars。 第一个which引导的定语从句修饰的是sharp metal bars。

First it will pass through sharp metal bars which will tear open the plastic bags in which rubbish is usually packed.

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该句子的主干是voices now come from many quarters；句首Just as结构做比较状语，意为"正如...一样"；insisting 引导的分词结构做定语修饰主语voice，分词结构中含有两个并列的由that引导的宾语从句，第二个宾语从句的真实主语是不定式结构to keep... 翻译：就象吸烟问题一样，来自不同领域的声音坚持认为有关全球变暖的科学资料还不完整。

Just as on smoking, voices now come from many quarters insisting that the science about global warming is incomplete, that it's Ok to keep pouring fumes into the air until we know for sure。

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目前，研究人员猜测梦是大脑情感自动调节系统的组成部分，当大脑处于“掉线”状态时对情绪进行调整。 【析句】Suspect后面是that引导的宾语从句；逗号之后的现在分词短语regulating moods…作定语，解释thermostat 的意思，句末的while引导一个时间状语从句。

Now researchers suspect that dreams are part of the mind's emotional thermostat, regulating moods while the brain is “off-line”.

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