Please, explain for me.

the 叫做 definite article，當我講o既時候你知我係講緊邊個，就要加 the。如：
He had a dog. The dog was called Snap.
如果唔係指明係邊ｄ，就唔用 the，如：
I don't like dogs.
你呢句 ... the concentration of carbon monoxide 當然冇指明係邊ｄ，因為你講緊o既係任何地方o既一氧化碳o既危險濃度，係一個標準。
... less than one hour of continual operation... 亦冇指明邊一次 operation，而係部機器因為構造而每次都會發生o既情況。
... of the petrol-fuelled generator 當然係指明邊部機器啦，如果唔係個 test 做o黎做乜？

2007-06-12 11:50:25 補充：
順路睇埋：... the result... 係講文中個 test o既結果，所以係指明左；... the "Immediately Dangerous to Life or Health" concentration of carbon monoxide ... 係指明邊個一氧化碳濃度水平，而 life 同 health 係講普遍人o既生命健康，所以唔係指明。即係話其實所有名詞都係用呢個方法決定，同文中位置無關。

有冇the同前面個 of 冇關係0架喎，the係用0黎表示"指定"或者文章之前提過0既"0野"，例如：I just bought a new shirt and some new shoes. The shirt was quite expensive, but the shoes weren't. "the" 0係句入面係指定你買0左嗰件衫同嗰對鞋，所以用the。同前面任何0既preposition冇關係0架喎。

而幾時應該要有the呢，就係睇0下樣0野係咪畀指定0架喇，好似文字中0既"the result" 係指佢為測試carbon monoxide個test 0既結果，係指定呢一個test 0既結果，唔係其他test 0既結果，而concentration of carbon monoxide點解冇the呢，因為carbon monoxide係冇記認0既，每粒carbon monoxide都係一樣，所以就唔用the。