Among the most important are sulphate aerosols: tiny particles produced by the combustion of coal and some sorts of oilthat float in the air, sully the lungs, kill millions—and also, by reflectingaway incoming sunlight, cool Earth.

這個(gè)冒號(hào)的意義是做講解緣由？這個(gè)冒號(hào)后面是詞還是句子，決定了后面這個(gè)加粗部分是多重定語(yǔ)從句修飾的詞？還是一個(gè)定語(yǔ)從句修飾的句子？假如不是多重定語(yǔ)從句，produced第一個(gè)定語(yǔ)從句用過(guò)去分詞的非謂語(yǔ)形式正好省略了which is，符合多重定語(yǔ)從句省略第一個(gè)定從的規(guī)則呀。

所以假如aerosols后面的冒號(hào)假如改成逗號(hào)，這句話是否就不成立了?

冒號(hào)后為一個(gè)名詞詞組，是前面名詞sulphateaerosols的同位語(yǔ)。這個(gè)名詞詞組的中心詞為 tiny particles，中心詞被過(guò)去分詞短語(yǔ)produced by the combustion of coal and some sorts of oil 修飾，然后tiny particles produced by the combustion of coal and some sortsof oil 作為先行詞被that引導(dǎo)的定語(yǔ)從句修飾。因?yàn)檫^(guò)去分詞短語(yǔ)不可以剖析為定語(yǔ)從句，所以這個(gè)句子中只有一個(gè)定語(yǔ)從句，并沒(méi)多重（雙重）定語(yǔ)從句，但你可以說(shuō)名詞tiny particles被雙重定語(yǔ)修飾。假如你把過(guò)去分詞短語(yǔ)改為定語(yǔ)從句，再把后面的that改為which，就得到雙重定語(yǔ)從句了。比如：

Among the most important are sulphate aerosols:tiny particles that are produced by the combustion of coal and some sorts of oil which float in theair, sully the lungs, kill millions—and also, by reflecting away incomingsunlight, cool Earth.