a 150-year history 还是 an 150-year history

a 150-year history 还是 an 150-year history xx-year history前面为什么是+a/an的? 70-year history Chinese New Year History. China is an old country with a 5000-year history.（同义句） 是an history class还是a history class? He worked in a big history m____ last year. a four-thousand-year history 与 four thousand years' history哪 my uncle is a history.he teaches us ___ history this year (c 1.The year 1066 was a ____ year for England.(history) on that day of a year do soldiers star wars in history Archery has a 10,000-year history,when bows(弓) and arrows(箭)