例199　The brain finds it best to keep smell receptors available for unfamiliar and emergency signals such as the smell of smoke, which might indicate the danger of fire.

【结构分析】这句话是形式宾语it，真正的宾语是不定式to，主干是The brain finds it best to keep smell receptors available，后面加上介词短语for unfamiliar and emergency signals，后面再加上介词短语such as the smell of smoke，后面加上定语从句which might indicate the danger of fire。

【亮点回放】此句话的亮点在于形式宾语加上定语从句的超级组合，很有气势。

【核心词汇】

the brain　大脑

smell receptors　味觉接收器

unfamiliar and emergency signals　不熟悉的紧急信号

danger of fire　火灾的风险

【参考译文】大脑发现最好让味觉接受器可以用来识别陌生的紧急信号，比如烟的味道，这种味道意味着火灾的风险。