xx-year history前面为什么是+a/an的?

xx-year history前面为什么是+a/an的? 70-year history Chinese New Year History. Yesterday becomes history 为什么不需要在history前面加a 可数名词前面不是都要加a或an吗 the computer is the most important invention in human history这里的history前面为什么不加the?那the history of china都有加the的呀 the year before last.year 为什么要放在before last的前面. 蚕有几只脚前面xx对,后面xx对 Which do you like best,history,English or Chinese为什么这里的best前面不加the? at this time of year的year前面为什么没有冠词需要谁能给出详尽的解释 After_____silence,they began to write to each other.A a three-year B three-year 感觉three-year 就可以了,为什么前面要加a呢? 是what year are you born还是which year are you born?为什么？那要是就在Year前面有一个空，要填什么呢？ China has_________history.A.5000-year B.5000 years’ 为什么?A答案是个复合形容词，为什么不可以修饰后面的名词history？ XX地的前面是什么词 S990银前面的XX是什么意思 S990银前面的XX是什么意思 在答案前面加题号,如1.xx He 什么 （read ）many books about history last year He worked in a big history m____ last year.